现代车辆制动机应具备哪些条件？

--Did you finish your homework on time yesterday.

--No, I didn't _______ on time. By the time I finished it, all my classmates

A．finish it; turned it in

B．finish it; had turned in it

C．make it; turned it in

D．make it; had turned it in

在t℃时，将10g某纯净物完全溶解在90g水中，你认为所得溶液中溶质质量分数可能出现哪几种情况？试举例说明．

在一个电场中，把电量为2.0×10^-9C的带正电的检验电荷，从A点移到B点，电场力做正功1.8×10^-7J．

求（1）AB两点的电势差U_AB

（2）取A点处电势为零，求B点电势及检验电荷在B点的电势能．

“客户交易结算资金第三方存管”业务的服务对象仅限于与我行签订协议的（）（包括个人与机构投资者）。

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