—That's quite a long time. There must be too many people waiting in line.
A:took
B:to take
C:take
D:taking
如图是DNA片段的结构图,请据图回答:
创立大陆漂移学说的科学家是( )
实验室有两瓶失去标签的无色溶液,一瓶是稀硫酸,另一瓶是氢氧化钠溶液.下面是四位同学提供的四种试剂,其中不能将它们鉴别出来的是( )