—_____ many of you good at _____ ?

—No, only he _____ .

A. Does; swimming; does                  

B. Are; swim; are      

C. Are；swimming; is                      

D. Is; swimming; is

做单元生产线的时候，生产处于无序状态，由于工程和物料的原因，无法精确估计产能？