题目

—Have you finished your research essay? —I haven't started yet. I ________ relevant materials the whole of last week. A . have collected B . was collecting C . would collect D . had collected 答案：B“落红不是无情物，化作春泥更护花，根据生态系统各组成成分的功能可知，将“落红”化作 “春泥”的是A、生产者 B消费者 C、分解者 D.阳光