Helen is ______ office worker in a big company near Xinjiekou.
A:a
B:an
C:the
D:/
下列因果关系正确的是( )
已知变量x,y满足约束条件y≤2x+y≥1x-y≤1,则z=3|x|+y的取值范围为( )
There are five birthdays in July. (对划线部分提问)
____birthdays ____in July?
根吸收水分和无机盐的主要部位是根尖的( )