Under no circumstances ________ the door to the Data Centre unlocked.—I promise I’ll be more careful in future.

It is becoming more and more difficult to ____ the problems of traffic in some big cities of our country.

All the students are looking forward to the first ________ to take the College Entrance Examinations.

is of no importance to great thoughts, ________ are as fresh today as when they first passed through their authors’ minds, ages ago.

I argued with my best friend yesterday,____ he was still willing to help me.