Every possible means ________ to prevent the air pollution, but the sky is still not clear. [ ]

always been honest and straightforward,and it doesn’t matter ___ I’m talking to

Can you come up with another good idea—This is the best approach I can imagine __________the work ahead of schedule

.—When shall we go to watch the basketball match in the sports center—Not until the work ___tomorrow.

Why does Sara know so much about Angkor Wat? 　 —She ____ have been there, or… [ ]