1. 有關Not one of...後接單複數的問題 "none" can actually go either way, but the preferred usage of "none" is singular.
2. 有關if子句的的角色 it appears that an "if" clause is allowed to act as a modifier. in this sentence, the "if" clause is quite clearly modifying the word "penalties".
i wouldn't go so far as to say that an if-clause can modify _any_ noun, but you can at least deduce that if-clauses can modify nouns in the same capacity as the noun in this problem - i.e., nouns describing some sort of potential consequence of something.
so it's not just penalties; you could say "consequences if ...", or "sanctions if the papers are filed late", or "bonuses if your performance exceeds this quota", or any number of other, similar constructions.
MGMAT的Tim回答C選項的"be signed" 錯誤原因 In this case, i think they used "be signed" to trick you into thinking of the command subjunctive. Of course, that's not what C was all about, which is one of the reasons why C is wrong..