It is generally considered unwise to give children ________ they wants.

A．however

B．no matter how

C．whatever

D．no matter what

有关材料层的导热热阻，下列叙述中哪一种是正确的？

A．厚度不变，材料层的热阻随导热系数的减小而增大

B．温度升高，材料层的热阻随之增大

C．只有增加材料层的厚度，才能增大其热阻

D．材料层的热阻只与材料的导热系数有关