要观察肝组织中的细胞类型及排列，应先制备该组织的（）
A、滴片
B、切片
C、涂片
D、印片
参考答案：B
Li Ming's father ____________ wears skirts.[ ]
A. always
B. usually
C. sometimes
D. never
There _____ five chairs under the tree. [ ]
A. /
B. is
C. am
D. are
