The sheep ----farmed for meat by theold man,which is said to ----by a scientist yesterday.A is；be bought B are；be bought C is；have been bought D are have been bought为什么选C

Question

The sheep ----farmed for meat by theold man,which is said to ----by a scientist yesterday.
A is；be bought B are；be bought C is；have been bought
D are have been bought
为什么选C

Answer 1

那个老头养的用来吃肉的那头羊,据说昨天被一个科学家买去了.
因为,which is 用的是单数,判断前者用单数.
因为已经被买走了,所以用了不定式的完成式