Is_____ necessary ____them to stop ________ every two hours?
Liu Dehua, Zhou Jielun and Lin Junjie are famous _____ their pop songs.[ ]
I have tried very hard to find a solution to the problem, but in vain —-why not consult with Frank? You see, _________.
Have you ________ watched the dolphin show in the Ocean Park in Hong Kong?—Not _________.
There _______ a football match this evening. —Exciting news.