This novel is set in the modern city, San Francisco, so once_______, it will be very popular.

A．publishes

B．having published

C．publishing

D．published

熔化极氩弧焊在氩气中加入（），可以有效地克服焊接不锈钢时的阴极飘移现象。

A、一定量的氮气

B、一定量的氢气

C、一定量的CO

D、一定量的氧气