与金属导体电阻无关的因素是()。
A.导体长度;
B.导体电阻率;
C.导体截面积;
D.外加电压。
参考答案:D
下列活动可以改变非洲国家“单一商品经济”的是
A.出口可可
B.出口咖啡
C.出口菠萝
D.发展农产品加工业
—Why was the headmaster in our school very pleased?
—Because the students in our school ________a Green City Project last year.[ ]
A. set out
B. set off
C. set up
D. send up