—Why do you look so puzzled?—Oh，I ________ over a most difficult maths problem.

Daniel, you really should cut down on sweets. You ______ fatter every time we meet.

Shanghai, China’s biggest and the most dynamic city, which______ in the Yangtze River Delta, is playing a leading role in the country’s economy. 

We are trying every possible means to ____ the people who are trapped in the ruins caused by this terrible earthquake.

— Have you been here before?— Yes. This is the third time that I ______ to Shanghai.