The pair of words "buy" and "sell" are ______.

单项选择题It is taken as a great contribution made by _____ that languages in the world are classified into different language families according to their genetic relations.

单项选择题The largest lake in Britain is ______.

单项选择题The Romans leaded by______ came with 10,000 soldiers and landed on the shore of Kent in 55B. C.

单项选择题Walt Whitman was a pioneering figure of American poetry. His innovation, first of all, lies in his use of ______, poetry without a fixed regular rhyme scheme.

单项选择题Among the great Middle English poets,Geoffrey Chaucer is known for his production of ______.