—You will break down if you keep on doing like that.

—______, but I just want a good result in this exam. [ ]

A. Thanks a lot                

B. Don’t mention it

C. You’re welcome            

D. Sounds great

常物性流体管内受迫流动，沿管长流体的平均温度，在常热流边界条件下呈线性变化，在常壁温条件下呈（）变化。