题目

---Alice, what’s wrong with you? You look so worn out． ---Nothing serious．I        my new house all day and I’m afraid I won’t finish until tomorrow afternoon． A．have whitewashed                                       B．am whitewashing C．have been whitewashing                              D．shall be whitewashing欲观察细胞减数分裂的过程，可选用的材料是 A．马蛔虫受精卵       B．蝗虫的精子          C．小鼠睾丸            D．鸡的血液