单项选择题 It is very convenient to pay by（）card.

单项选择题 His wife is a（n）（）housekeeper.

单项选择题 The fields were（）every year by the run-off water from the mountains.

单项选择题 The picture（）the seriousness of pollution on our planet.

单项选择题 The heat in the（）air rising from the kitchen and bathroom is recovered by the pumps.