Most air pollution is caused by the burning of _________ like coal, gas and oil. 

Haier Company produced a new type of refrigerator of high quality and pretty appearance; its only ___is that it takes up too much room. 

Mr. Li doesn’t think that all bad language should be allowed. In his opinion, there are ______ that should be kept up.

Burning all the lights in the classroom will be a great______ on electric power.

American artist Jeremy Telford made a room with balloons． He got the____    from Bag End in Lord the Rings, which is a hole in the ground where a Hobbit（霍比特人）lives in the film．