1.He was a good swimmer,so he__swim to the bank when the boat turned over.

1.He was a good swimmer,so he__swim to the bank when the boat turned over.
A.was able to
B.could
答案A.表示过去特定情况下的能力,只能用 was [were] able to,不能用 could.turn over的意思是“翻船”.
2.-Tom,you are caught late again.
-Oh,___________.
a.not at all
b.just my luck
c.never mind
d.that's all right
选B,not at all的意思是“没关系”,just my luck的意思是“只是我运气不好”,never mind的意思是“没关系”,that's all right的意思是“没关系”.
3.A fence__our garden___the playing field.
A.divides;into
B.separates;into
C.separates;from
D.divides;from
答案C.separate 和 divide的区分：
两者均可表示“分开”：divide 通常指把整体分为若*分,其后常接介词 into；而 separate 通常指把原来连在一起或靠近的东西分隔开来,其后常接介词 from.如：
The world is divided into seven continents.世界被分成七大洲.
We’d better separate the good ones from the bad ones.我们最好把好的和坏的分开.
4.____your mother,I found her healthy and she had me tell you to work hard.
A.Delighted to see
B.Delighter to have seen
C.Delighting to have seen
选B.但答案中的 Delighter 应为 Delighted.因为是“感到高兴”,故不能和 delighting,排除C；又因为“已经看到了”,所以要用完成式,故选 B,不选 A.