.Gun control is a subject _____ Americans have argued for a long time.
150. He was never late for school, _______ more than once by the class teacher..
151. Oh, it is so cool in the house. You _______ have turned on the air-conditioner, haven’t you?
152. The residents approve of the measure ______ so far in our city, _____ to bring a sharp rise in oil prices.
153. Though our city has a good public transport system, _____ private car is becoming _____ popular means of transport.
154. Using renewable energy is a simple idea, but ______ we find it hard to put into practice.