变压器（电抗器）油中溶解气体主要监测的缺陷是（）
A.受潮
B.铁心多点接地
C.内部过热
D.放电
参考答案：A, B, C, D
.
We often talk a great deal about English language teaching, _____ that it is the learning that really matters.
A．having forgotten
B．forgotten
C．forgetting
D．to have forgotten
公钥密码体制与对称密码体制相比有什么优点和不足？
