He tried to deal with the ever-increasingburden of his work，butfinally _____ and had to take a complete rest

Even if these chemicals are still in experimental stages, they _____ to be a number one hit.

My father _________ Beijing many times. He _________there again last week.

The rescue team didn’t leave until they were able tofind no ______ of life in the ruins after the destructive quake.

listening to the concert, theaudience is required to remain ______ and keep quiet.