1,John said his mother would buy him a five-speeds racing bicycle for his sixteenth birthday.
像five-speeds這種數(shù)詞+名詞構成的合成詞或詞組作另一個名詞的定語是,只能用單數(shù)形式,所以要改為：five-speed racing bicycle
2,By reading the directions carefully,some mistakes in the examination could have been avoided.
此題中的could have been avoided是虛擬語氣,而本句所表達的意思并非與事實相反,by...表示“通過...方法”,那么其后的“避免”是一個必然的事實,因此應改為：could be avoided,
3,I can't help to think it would be fun to play such an exciting game with them.
can't help（禁不?。┖竺娴姆侵^語動詞賓語要求動名詞,應改為can't help thinking
4,Of the tew lectures,the first was by far the best one ,partly because the person who delivered it had such a pleasant voice.
既然是two lectures,就只能用比較級,所以by far the best one 中的the best應該為better.
5,The chairman proposed that every speaker must limit himself to fifteen minutes.
本句表示主語（The chairman）的愿望,因此后面的賓語從句要用虛擬語氣,因此must limit 應該把must去掉.
6,When I got to the cinema ,the film had already started;I ought to get there earlier.
I ought to get there earlier是前面句子并列的主句,時態(tài)應保持一致,因此應該是I ought to have got there earlier.
7,After criticizing our proposal in every detail,the director went on telling us that there was nothing personal in his comments.
criticizing our proposal 與telling us 時兩件相接的不同話題,而go on doing表示的是繼續(xù)同一個話題,因此應該是go on to tell,即接下來繼續(xù)另一個話題.