—Have you brought _______ with you? We won' have time to come back.    

—Don' worry. All the things we need are here, in this big bag.[ ]

A. something    

B. anything      

C. nothing      

D. everything

作物对水分最敏感的时期，即此时水分过多或不足对作物产量影响最大，称为该作物的______。