【单选题】神经冲动在神经元之间的传递是借助( )实现的。
A. 突触
B. 轴突
C. 髓鞘
D. 树突
【单选题】人的周围神经系统包括( )。
A. 大脑和脊椎
B. 大脑和小脑
C. 脑神经、脊神经、植物性神经
D. 脑神经、脊神经
They opened a new store in our city, but not until last week ______ it.
A. we visited
B. we would visit
C. did we visit
D. have we visited
If you have difficulty ______ your bills, tell your utility company as soon as possible.
A. pay
B. paid
C. to pay
D. paying