氢原子能级图如图所示，a,b,c分别表示原子在不同能级之间的三种跃迁途径，设在a,b,c在跃迁过程中，放出光子的能量和波长分别是和，若a光恰能使某金属发生光电效应，则

A．

B．=+

C．

D．C光也能使该金属产生光电效应

The external auditing shall be conducted by the Customs over the following enterprises and other organizations （）.

A. Enterprises and other organizations engaged in foreign trade only

B. Enterprises and other organizations engaged in domestic trade only

C. Enterprises engaged in the business of inward process only

D. Both A and C