如图,如果∠AOB=∠COD=90°,那么∠1=∠2,这是根据( )
A:直角都相等
B:等角的余角相等
C:同角的余角相等
D:同角的补角相等
如图所示,为了测定“额定电压2.5V”的小灯泡额定功率的装置.要求:
When she heard her son had been admitted to a key university,words couldn't ________ her excitement.