下列短文中有十个空白，每个空白有四个选项。根据上下文要求选出最佳答案，并在答题纸上将相应的字母涂黑。
One type of solar collector is not very expensive. It is usually 11 on the sunny side of the roof of a building. The sun is most _12 on this side,and the unit will 13 more heat from the sun. The unit has a 14 or level surface. The surface is black because black collects more heat from the'sun. 15 ,there are pipes with water. The top is a piece of glass. The sun 16 through the glass and air inside. It heats the 17_ that is also inside. A pump,a machine to 18 the water,stafls when water is warm enough. The hot water goes into a storage tank. This tank 19 or keeps the hot water. Then there is hot water to use for washing clothes or 20baths and showers.
11. A. pushed B. pulled C. pressed D. put
12. A. direct B. opposite C. negative D. steep
13. A. assemble B. swallow C. reflect D. collect
14. A. broad B. narrow C. flat D. short
15. A. Outside B.lnside C. Upside D. Downside
16. A. shines B. burns C. heats D. brightens
17. A.air B.water C.liquid D.light
18. A. move B. remove C. obtain D. maintain
19. A. stores B. weighs C. yields D. traps
20. A. take B. took C. taking D. takes
