两根阻值比为R1:R2=1:2的电阻丝通过的电流之I1:I2=2:1,在相同的时间内,它们所放出的热量之比Q1:Q2为( )
A.1:1
B.1:2
C.2:1
D.4:1
答案:C
Mother was in the kitchen ______ lunch while I was ______ the coming exam.
A.prepared; prepared for
B.preparing; preparing for
C.prepared for; prepared
D.preparing for; preparing
最高额担保