_    we were walking along the river, we heard a cry for help.

______hours do you exercise every week ?  Nine hours.

Frank often wears a mask ________he can keep fit in the foggy and hazy (霾) weather.

Not only English but also maths _______ my favourite subject.

—Is it interesting to play computer games?—Yes, _____ you are interested in playing computer games, you’ll have trouble giving it up.