The bookstore has sold _______children’s books as they did last year.

A．twice as much

B．twice as many

C．as twice many

D．as twice much

如图所示，变频交变电源的频率可在20 Hz到20 kHz之间调节，在某一频率时，A₁、A₂两只灯泡的炽热程度相同．则下列说法中正确的是( 　　)

A．如果将频率增大，炽热程度减弱、炽热程度加强

B．如果将频率增大，A₁炽热程度加强、A₂炽热程度减弱

C．如果将频率减小，A₁炽热程度减弱、A₂炽热程度加强

D．如果将频率减小，A₁炽热程度加强、A₂炽热程度减弱