The web is fantastic at many things—e-mail, e-commerce, for example. But ________ your name is Amazon or Google, making money has proved hard.

A．if

B．unless

C．although

D．as long as

在二极管桥式整流电容滤波电路中，若有一个二极管接反，将造成（）。

A.半波整流

B.短路，损坏元件

C.断种，不能工作

D.短路