甲醇合成催化剂在装填时,应注意的事项有()。
A、催化剂要过筛除粉
B、避免在潮湿的环境中装填
C、需在潮湿的环境中装填
D、装填要缓慢,防止破碎
参考答案:A, B, D
______clearly in class, Mr. Smith raised his top voice to ask his students to stop chatting.
A.Found not heard
B.Found not hearing
C.Finding not heard
D.Finding not hearing
简述器械性人工流产的适应症和禁忌症。