— Mom, I found that my book open on Jack's desk last night.
— Really? I couldn't believe that he to me yesterday.
A:lay; lie
B:lie; lied
C:lied; lied
D:lay; lied
4辆板车和5辆卡车一次能运27吨货,10辆板车和3车卡车一次能运货20吨,设每辆板车每次可运x吨货,每辆卡车每次能运y吨货,则可列方程组( )