通常用于丝虫病普查的方法是（）.
A.薄血膜涂片法
B.厚血膜涂片法
C.浓集法
D.海群生白天诱出法
E.皮内试验
参考答案：B
Mrs Smith ______ a teacher. But she doesn't do that job now. [ ]
A. used to be
B. was used to be
C. has been
D. was used to doing
