[Grammar] If possible, could I...?

[kaeman]

Hi, pardon a newbie question, but I need to describe the grammar behind the request: If possible, could I...?

'If' is the conditional and is followed by the adjective, "possible", so it is a 'conditional adjective phrase' - if such a thing exists?

I am making some multiple choice grammar questions and my Japanese students will want to know the grammar behind them. In the question below, what is the grammar explanation behind the correct answer?

2) If [ ], could I…?

correct: possible

incorrect: possibly

incorrect: is possible

Thank you in advance.

 

[TheParser]

***** NOT A TEACHER *****

Raul: If possible, could [can] I borrow $100 from you?

Mona: What did you say? That jet flying overhead made so much noise that I couldn't hear you.

Raul: I said: if it is possible, could I borrow $100 from you?

Mona: Of course, it is possible. In fact, I will give you $100. I never lend money to a friend, for I don't want that friendship to end.

*****


I believe that most secondary school grammars would classify "If [it is] possible" as an adverbial clause.

 

[MikeNewYork]

"If possible" is a phrase, not a clause. If one inserts "it is" it becomes a clause.

 

[Matthew Wai]

what is the grammar explanation behind the correct answer?

Could the following be the explanation?

The adjective 'possible' cannot be changed to the adverb 'possibly', and the preceding verb should be omitted together with the subject.