微观调查范围小，调查对象比较（）。
A、复杂
B、单一
C、凌乱
D、协调
参考答案：B
He ________the shop while the manager was away.[ ]
A. was left in charge of
B. left in charge of
C. was left in the charge of
D. left in the charge of
尿沉渣常规检查时，标本制备离心处理所需相对离心力约为( )
A．200gB．400gC．500gD．800gE．1500g
