All the preparations for the task________,and we're ready to start. A.completed B.complete C.had been completed D.have been completed 答案:D考查动词时态。用现在完成时表示过去所做的事对现在的影响。所提供的情景and we're ready to start(我们正准备开始)表示一切工作已经就绪,可以开始工作了。 做实验时,区别蚯蚓前端和后端的主要依据是( )A.体节 B.刚毛 C.环节 D.环带