17. - "Here’s my phone number".
- "Thanks. I’ll give you a call if I __________ some help tomorrow".
A. will need B. need C. would need D. needed

18. The patient will not recover unless he __________ an operation.
A. had undergone B. would undergo C. undergoes D. was undergoing

19. If it __________ convenient, let’s go out for dinner tonight.
A. be B. is C. was D. were

1.  

"Here’s my phone number."
"Thanks. I’ll give you a call if I need some help tomorrow."
Correct answer: B. need
Explanation: In this conditional sentence (if clause), we use the present simple tense to refer to a future possibility.
The patient will not recover unless he undergoes an operation.
Correct answer: C. undergoes
Explanation: "Unless" is used with the present simple to indicate a condition that must be met for something to happen.
If it is convenient, let’s go out for dinner tonight.
Correct answer: B. is
Explanation: This is a first conditional sentence, which uses the present simple tense (is) to talk about real, possible future events.