双端直流输电系统的主要接线方式有()。
A.单极大地回线
B.单极金属回线
C.双极大地回线
D.双极金属回线
参考答案:A, B, C
Jack failed to seek a job for his poor education, though he was ____to get one to support his family.
A.dying
B.looking forward
C.fighting
D.wanting
工程质量问题的表现形式千差万别,当工程质量事故发生后,应及时调查处理。调查的主要目的,是要确定事故的()
A.范围、责任、影响和原因
B.范围、性质、严重程度和原因
C.范围、性质、影响和原因
D.范围、性质、影响和后果