______many times ,he finally undertood it.A.Told B.Having been told

______many times ,he finally undertood it.A.Told B.Having been told
1._many times,he finally understood it
A.Told B.Having been told B
2._time,the postman refused to deliver our letters unless we chained our dog
A Bitten B.Having bitten
为什么这两道题不一致呢,既然第二道题用bitten,第一道题为什么不用told