Ⅳ. 用所给词的适当形式填空
【小题1】You should do sports every day __________ (keep) fit.
【小题2】The doctor advised my uncle to stop __________ (work) immediately and have a rest.
【小题3】It's impossible __________ (learn) English well in a short time.
【小题4】Please be careful of __________ (fall) stones during an earthquake.
【小题5】__________ (not smoke) here, Rick. Smoking is not allowed in public places.