We thought of selling this old furniture,but we've decided     to________ it. It might be valuable.    

[ ]

A. hold on to                    

B. keep up with      

C. turn to                              

D. look after

影响浓缩的因素有（）

A.传热温度差

B.传热系数

C.蒸气压力

D.物料性质

E.蒸发器生产强度