容量瓶如何试漏?
参考答案:
在瓶内装入自来水到标线附近,盖上塞,用手按住塞,倒立容量瓶,观察瓶口是否有水渗出,如果不漏,把瓶直立后,转动瓶塞约180°后再倒立一次。
I didn’t like Aunt Lucy, who______without warning and bringing us presents.
A.always turned up
B.has always turned up
C.was always turning up
D.was always turned up
简述源控理论的基本思想。