It's so kind of you to help us. Without your help, we couldn't have finished the work___________.    

[ ]

A.in a time                      

B. at no time    

C. ahead of time                  

D. behind time

一定量的盐酸跟足量的锌粉反应时，为了减缓反应速率，且不影响生成氢气的总量，可向盐酸中加入适量的（　　）

A．NaOH溶液

B．NaNO₃溶液

C．CuCl₂溶液

D．KCl溶液