【简答题】电荷的 形成电流,形成持续电流的条件是 和 。
【简答题】电荷的____形成电流。形成持续电流的条件是____和____。
【单选题】The mining industry in the U.S. became safer after the late 1960s because
A.
the U.S. Senate passed laws requiring federal mine inspections.
B.
the U.S. Congress passed laws requiring federal mine inspections.
C.
the U.S. health and safety officials passed laws requiring federal mine inspections.
D.
the U.S, mine companies passed laws requiring federal mine inspections.
【单选题】Laws requiring computer companies to pay for recycling their products have been passed for the purpose of ( )
A.
urging them to design upgradeable equipment
B.
cutting down their costs of production
C.
reducing the number of computers to be produced
D.
encouraging them to advertise their products
【简答题】汽车制动系统一般包括 和 两套相互独立的制动系统,每套制动系统都包括 和 。A. 行车制动系统、驻车制动系统、制动器、制动传动机构
【简答题】形成持续电流的条件是 ________ 和 ________ 。