You may lead the horse to the river, but you _____ make it drink.

What on earth are the police busy with— They have been investigating how the train crash __________

Checking your answers before handing in your paper can help you mistakes.

f the treatment _____, there’s still no magicpill for patients in the late stage of AIDS.

Tom, did MrLi join you in your discussion? —- No, he _____, but he happened to have fallen ill