濒临三大洋、地跨两大洲,并有极昼、极夜现象的国家是
①俄罗斯 ②加拿大 ③挪威 ④美国
A.①②
B.③④
C.②③
D.①④
答案:D
I have made ______ clear _______ I have nothing to do with the accident.
A.it; what
B.that; that
C.it; that
D.this; that
电力系统自动重合闸有什么好处?