@weiwei,
There is always a heading on the label:
Directions For Use.
It should be 'directions', which you give in your INTRODUCTORY sentence, but do not list in your alternatives.
'directions' might be as simple as "Take 2 tablets every 6 hours".
'instructions' = (often detailed) information about what is to be done, or how something should be done; with the added meaning of 'direction', this has the sense of an order!
I have never see the word 'Instructions' on any kind of medicine; but maybe if I had ever taken MAO Inhibitors or some such, that can have fatal results if certain guidelines are not followed, then, maybe, they might say "Instructions".
So: if 'directions' was NOT one of the alternatives, I consider the question is at fault, and I would HAVE TO give the answer as a given alternative, "Instructions".