我国药典对片重差异检查有详细规定，下列叙述错误的是（）。

A.取20片，精密称定片重并求得平均值

B.片重小于0.3g的片剂，重量差异限度为7.5%

C.片重大于或等于0.3g的片剂，重量差异限度为5%

D.超出差异限度的药片不得多于2片

E.不得有2片超出限度1倍

Remove the batteries when they become weak or when the unit is not in use for extended periods. This will           damage to the unit from battery leakage at such times.   

A．disappoint

B．concern

C．instruct

D．prevent