Could you please me with three single-choice questions on my test paper?
1: All the members of the jury believed what the witness said was ( ).
A credible. B credulous
C reliable. D trustworthy

2: I think hes deceiving you with. ( ) promises.
A vain. B. void
C empty. D hollow

3: His professor thought his vocabulary was ( ...) for the clear and forceful statement of his ideas.
A. sufficient. B adequate
C. much. D enough

Thanks in advance for helping, it would be wonderful If you could offer to explain a bit the reasons.

Question

Could you please me with three single-choice questions on my test paper?
1: All the members of the jury believed what the witness said was (      ).
A credible.        B credulous 
C reliable.          D trustworthy

2: I think hes deceiving you with.   (       ) promises. 
A vain.       B.  void 
C empty.    D hollow

3: His professor thought his vocabulary was (     ...) for the clear and forceful statement of his ideas. 
A. sufficient.      B adequate 
C.  much.            D enough

Thanks in advance for helping, it would be wonderful If you could offer to explain a bit the reasons.

Answer

1A   A jury has to believe that what a witness says is the truth. So the witness has to be credible.

2. C The normal saying is empty promises. This means that the promise has no substance, it is a lie.

3. b adequate.   Sufficient means that the person just has enough words. Much would not fit as an English expression. Enough is related to sufficient in this context.

You really should come to your own answers if your purpose is to learn English.