My English teacher has _____ 8 year-old girl called Mary.[ ]
A. an
B. a
C. the
D. /
答案:A
给你一个圆,你能至少用几种方法找到圆心?
单个样品量足够的随机对照试验结果属于
A.一级证据B.二级证据C.三级证据D.四级证据E.五级证据