He stared at the empty bottle for a while, feeling happy that he had sent the butterfly back ________ it belonged-nature. [ ]

A. to which  

B. that

C. which  

D. to where

评价外科病人的营养状态，最简单而实用的指标是（）

A.近期体重下降程度和三头肌皮褶厚度

B.血清转铁蛋白和视黄醇结合蛋白

C.握力和三头肌皮褶厚度

D.近期体重下降程度和血浆白蛋白水平

E.氮平衡试验