When a new disease breaks out，experts mustwhat to do in the fastest way．

— Can Ienter the laboratory,sir?— Under no circumstances________to enter it without approval. [ ]

It’s time you _______ some reading or the other students will leave you behind.

To avoid on how to use the word, you’d better refer to a dictionary. [ ]

______ to improve oral English, I make great efforts and spend as much time as possible practicing it.