题目

下列图示的实验操作中，正确的是                                  （    ） 答案：A用所给词的适当形式填空1. We're doctors, so it's our _______ (duty) to save patients.2. The road is _______ (crowd). Mr. Wang drives his car slowly.3. What causes the _______ (ill)?4. Did they enjoy _______ (they) in the party yesterday?5. —Where is your mother, Beibei?    —She is busy _______ (answer) the telephone.