傅里叶定律中的负号表示热流方向与()方向相反。
A.流动
B.导热
C.对流
D.温度梯变
参考答案:D
— Is this your mother?
— Yes, ___ .[ ]
A. she is
B. it is
C. it isn't
正方体的棱长是a,它的体积是3a.______.