Let's try to imagine some continuations for each move.

With move a, White is adding a stone to a group which is already quite strong; on the other hand, Black increases his moyo while swallowing the two white stones on a big scale.

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[go]$$Wc Move a
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X . X . . . X . . . . . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . 2 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . 1 X X O O X . |
$$ | . . O . . . . . . . . . O O O X X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . O , X X . O . O . . . . . O X . . |
$$ | . . . O O X . . . . . . . X O O X . . |
$$ | . . . . . . . O . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

With move b, White reduces Black's potential on the right side but needs to struggle a lot to survive, and allows Black to control the center.

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[go]$$Wc Move b
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X . X . . . X . . . . . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . 5 . . . . |
$$ | . . . . . . . . . . . . . 4 . 3 . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . 2 . 1 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . . X X O O X . |
$$ | . . O . . . . . . . . . O O O X X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . O , X X . O . O . . . . . O X . . |
$$ | . . . O O X . . . . . . . X O O X . . |
$$ | . . . . . . . O . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

With move c, White does reduce Black's potential on the top but also helps Black to build solid territory while attacking.

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[go]$$Wc Move c
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . 4 . 1 2 . . . . |
$$ | . . O X . X . . . X . . . 3 . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 5 . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . . X X O O X . |
$$ | . . O . . . . . . . . . O O O X X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . O , X X . O . O . . . . . O X . . |
$$ | . . . O O X . . . . . . . X O O X . . |
$$ | . . . . . . . O . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Hard to decide. I have a slight preference for c.

I think it has to be 'a' or 'c'. 'b' just creates a weak group to attack, with no obvious upside.

My shape autopilot says 'a'. I would call it thick (John?) and it casts a menacing glance towards the group on the left. Without the weakness on the left I'm not sure how good a move it would be, since I think there's also a danger it could be overconcentrated.

a is the sort of move I imagine a strong player yelling at me for not making.

At this point in my development, I try to make those moves without spending too much time trying to talk myself out of it.

A, the turn, leveraging the two disposable stones, creating a thick wall which will affect everything to its left, in particular Black's floating group.

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[go]$$W Best
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . c . . . . . |
$$ | . . O X . X . . . X . . . . . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . b . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . 1 X X O O X . |
$$ | . . O . . . . . . . . . O O O X X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . O , X X . O . O . . . . . O X . . |
$$ | . . . O O X . . . . . . . X O O X . . |
$$ | . . . . . . . O . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

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[go]$$W Mistake 7
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . c . . . . . |
$$ | . . O X . X . . . X . . . . . X . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . 1 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . 2 X X O O X . |
$$ | . . O . . . . . . . . . O O O X X X . |
$$ | . . . . . . . . . . . . . . d O O X . |
$$ | . . O , X X . O . O . . . . . O X . . |
$$ | . . . O O X . . . . . . . X O O X . . |
$$ | . . . . . . . O . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The important idea is that saving the two stones here is heavy. They cut the black center stones but don't affect anything else. Black can strengthen the center stones at the expense of White's development at the bottom and in the center, also taking advantage of the aji at D.

Turn like Shuko would. It's double sente to boot. In fact I find it odd that it is White's move in this shape: locally I expect White just extended (hane may have been better) and then black tenukid (top left block looks like possible place for the n bad timed gote) rather than keep on pushing.