单纯固定液属于剧毒品,是电镜研究的必需固定剂的是()
A.锇酸
B.三氯醋酸
C.苦味酸
D.醋酸
E.升汞
参考答案:A
I regret _____ you that Tom failed to pass the driving test and that he really regretted ______ your advice on practicing more.
A.to tell; not following
B.to tell; having not followed
C.telling; not to follow
D.telling; not having followed
当变压器的变比小于1时,变压器为()变压器。
A.升压
B.降压
C.隔离
D.双圈