既能平肝潜阳,又能息风止痉的药物是()
A.牡蛎、龙骨
B.羚羊角、钩藤
C.桑叶、菊花
D.牛黄、磁石
E.全蝎、蜈蚣
参考答案:B
People _________ rivers for transportation since the beginning of history.
A.used
B.have used
C.use
D.had used
变压器由哪些主要部分构成?