With economy developing at great speed, our city has _____ quite a few changes in recent years.
While____the dog,you should take care not to____.Otherwise,it may be dangerous to strangers.
Tom ____ skating, so he spends all his spare time on it.
Having retired(退休), he ______ the club for old men and plays chess every day there.
Neither of them knows the difference ________ the two and neither can we tell one ________the other.
At the meeting, the old man ______ some good advice about bringing down the market price of housing.