《铁路车站行车作业人身安全标准》规定，下车车速不得超过（）。
A、10km/h
B、15km/h
C、20km/h
D、25km/h
参考答案：C
—Millie, could you give me some advice? I don't know _____.
—Why don't you wear this red shirt? [ ]
A. when to wear
B. what to wear
C. how to wear
D. where to wear
列举八种常用的致突变试验？
