a) Where is this mentioned in the strategy guide regarding this idiom per se ? .....I am not sure i am seeing this under the idioms' chapter
We can't possibly list all the wrong idioms that GMAT will throw at you. We've picked out ones that we've found most common.
b) Are you saying the following statement is thus also false (i have the structure in bold)
In Country X, it is a crime that a citizen hold another citizen's arm in public
Yes, I mean that this sentence is grammatically incorrect.
2) It's mentioned that A and B are subjunctive
a) is this because of the structure --- THAT + United States citizen + hold ?
My point was that answers A and B
look like command subjunctive constructions, but are in fact incorrect.
b) If so -- is this wrong because A and B are missing bossy verbs (example : Demanded / Required / Mandate ......)
Yes, that's right: a correct command subjunctive construction needs one of those verbs.