拖式铲运机下坡时（）。
A.应低速行驶
B.不得空档滑行
C.不得转弯
D.不得制动
E.不得在档位上滑行
参考答案：A, B
It rained heavily this morning, but ______ of my classmates were away from school. [ ]
A. neither
B. none
C. all
D. both
婴幼儿鼻泪管________，开口部瓣膜发育不全，上呼吸道感染时易引起__________。
