by the time you finish your homework,all of us ------ ours at hand ,i am sureA will finish ,Bwill have finished ,Chave finished ,Dhave been finishing

by the time you finish your homework,all of us ------ ours at hand ,i am sure
A will finish ,Bwill have finished ,Chave finished ,Dhave been finishing

选B,这句话用的是虚拟语气,对将来事情的假设要用将来完成时态.
翻译：当你完成作业的时候,我确定,我们也将完成我们的了.

同意楼上。。你和我的动作都是将来时，体会一下

B. will have finished