紫外光对微生物有致死作用,波长为( )时就开始有了杀菌作用。
A.400nm
B.360nm
C.240~340nm
D.200~300nm
参考答案:B
请从下列选项中选出可以用来创建独立于时间轴播放的动画片段的元件类型()。
A.图形元件
B.字体元件
C.电影剪辑
D.按钮元件
In a nationwide poll, P people were asked 2 questions. If 2/5 answered "yes" to question 1, and of those 1/3 also answered "yes" to question 2, which of the following represents the number of people polled who did not answer "yes" to both questions ?()
A. 2/15 P
B. 3/5 P
C. 3/4 P
D. 5/6 P
E. 13/15 P