John is the only one of the students in the class that never ______ a mistake even when it is pointed to him.
I don't think the experiment is _____ failure. At least we have got _____ experience for our future work on _____ nature.
.He is really an excellent doctor and he is _____ to becoming an expert in this field.
The boy student is poor in health now; his parents wish that his health _____when he grows up
Don’t enter the office unless _______.
Can you find a sentence situation _______ this phrase can be used? A. where B. when C. which D. that