unit 4 二、单项选择 21. the sun heats the earth, ___________ is very important to living things. a. that b. what c. which d. where 22. he is a man with rich experience, from _______ much can be learned. a. whom b. which c. where d. what 23. ---what do you think made mar upset? --- ___________ her new bicycle. a. as she lost b. lost c. losing d. because of losing 24. we were ________when we heard of the news that the ship had sunk in the storm. a. shocking b. shocked c. worried d. worrying
