She _____ live alone. But she _____ living alone because she felt lonely. [ ]

A. used to; didn't used to

B. was used to; was not used to

C. used to; was not used to

D. was used to; didn't used to

表示在抽样调查中，一组样本的变异程度，即对均数的离散度的是

A．平均数
B．标准差
C．标准误
D．率
E．构成比