Here is the opening gospel according to LZ, play the following moves if possible in order from top to bottom (he negative ones are for urgent local situations):
-3) if your 3-4 is being pressed, answer
-2) if your 4-4 is 3-3 invaded, answer it
-1) if your 4-4 is double approached, attach out
1) play in empty corner
2) approach (low) or enclose (big high) a 3-4
3) press if they ignored your approach to 3-4
4) approach or 3-3 invade a 4-4
5) double approach a 4-4
6) enclose from 4-4

You will notice side moves are nowhere to be seen. Corners before sides, as the old proverb says.

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If your opponent attaches you - in general - should always answer because otherwise you'll get outnumbered in an area where you played first.

A or B seem fine.