－Jim, how about keeping a dog as a pet－Good idea! but I prefer to have a cat. The dog is _____ to look after.

It was about 600 years ago ______the first clock with a face and an hour hand was made[ ]

In those days, the old woman ________ sit at the door for hours, waiting for her son to return from abroad. [ ]

Some people plan to ______ a volunteer project to help the disabled children.

mous musician, as well as his students, _______ to perform at the opening ceremony of the 2012 Taipei Flower Expo.