— It's reported that the new underground line has been completed.

— Yes, but it hasn't been made clear _____ it's to be opened to traffic. [ ]

A. that

B. who

C. what

D. when

贮存、切割、清洗、出水、冷冻和受热过程往往会造成蔬菜中（）发生沥滤流失。