托盘操作分为（）两种。
A.重托/轻托
B.高托/低托
C.前托/后托
D.大托/小托
参考答案：A
— Where is Tom's and Peter's homework?
— The two students ______ ill yesterday, and they didn't come to school.[ ]
A. were all
B. all were
C. both were
D. were both
静吸复合麻醉
