在滑参数停机过程中，降温，降压应交替进行，且应先（）｡
参考答案：降汽温后降汽压
已知m﹣n=﹣5，m2+n2=13，那么m4+n4=( )
Good harvest this year has made it possible for us to supply walnuts ______ last year's prices.
A. at B. in C. against D. on
