《证券登记结算管理办法》规定证券登记结算机构不能要求高风险参与人提供交收履约担保。（）
参考答案：错
解析：熟悉证券交易结算风险的种类及其防范措施。
有甲、乙两导体，甲的横截面积是乙的2倍，而单位时间内通过横截面的电荷量，乙是甲的2倍，以下说法正确的是[ ]
A．甲、乙两导体的电流相同
B．乙导体的电流是甲导体的2倍
C．乙导体中自由电荷定向移动的速度是甲导体的2倍
D．甲、乙两导体中自由电荷定向移动的速度大小相等
It was announced that only when the fire was under control ___ to return to their homes. [ ]
A. the residents would be permitted
B. had the residents been permitted
C. would be residents be permitted
D. the residents had been permitted
