柴油机工作时的能量转化过程为()。
A.化学能→热能
B.热能→机械能
C.机械能→热能
D.化学能→热能→机械能
参考答案:D
小圆的半径是2厘米,大圆的直径是6厘米,大圆和小圆的周长比是( ),面积比是( )。
–Shall we go to the movie tonight?
--No, I’d rather ___ at home with our baby. You’d better not leave it to the babysitter at night.
A.you stayed
B.you stay
C.stayed
D.stay