The river is very wide.None of us ( A) swim across it .A.can B.could C.be able to D.able to
When the boat sank,he ( C )swim to the bank.
A.can B.could C.was able to D.is able to
can 和be able to 都有能、会的意思,但是be able to 有更多的时态变化形式,can 只有一般式和过去式形式,第一个题中要把C答案入选的话,应该是is able to ,第二个题中时态是过去式形式,它表示主语有能力做某事,我个人认为C 比B更合适些!