I was just going to cut my rose bushes but someone _____ it. Was it you?[ ]

A. has done        

B. would do        

C. will do          

D. had done

已知ρ_铁＜ρ_铜＜ρ_铅，用铁、铜、铅分别制成三个质量相等、体积相同的空心球，其中空心部分最大的是______．