单项选择题 进入轿厢的井道开口处应装设无孔的层门，门关闭后，门扇之间以及门扇与立柱、门楣和地坎之间的间隙应尽可能小，对于乘客电梯，此运动间隙不得大于（   ）mm。 A. 6 B. 8 C. 30 D. 50

单项选择题 In the US, baseball is still widely considered a national sport, although it lags behind football in popularity, it’s commonly referred as “America’s pastime”, which is also a popular game in Japan, Cuba and the Dominican Republic, and so on._________

判断题 最常见的诊断乳糖酶缺乏的方法叫做氢呼气试验。正确错误