滴定管使用前应做()等准备。
A.滴定管必须清洗干净
B.仔细检查有无渗漏情况
C.调整液面至零点
D.先放出部分溶液,而后检查滴定管内是否存在气泡
参考答案:A, B, C, D
The decorations were so lovely that they _____ in a short time.
A.sold out
B.has been sold out
C.were sold out
D.were selling out
测井过程中,测井深度编码器可以打开外壳在现场维修。()