Helen had to shout _____ herself _____ above the sound of the noise. [ ]

A. making;hear                              

B. to make;hear  

C. making;heard                              

D. to make;heard

用电器的额定功率是指用电器_________的电功率。用电器的实际功率是随着它两端的_________而改变的。例如标有“220V、60W”字样的灯泡接在110伏特的电路中，灯泡的实际功率是_________。