By the age of 40, some people are already experiencing breathlessness.(到40歲時，有些人已經感到氣絕。)

Even so, it admits that most children will have been infected by rotavirus by the age of 5.(既便如此，在5歲多數(shù)兒童已受輪狀病毒感染。)

By the age of 40, men's quality of sleep also begins to diminish.(大約在40歲左右，男子的睡眠質量就開始下降。)

A surprising discovery suggests our mental faculties have not yet been fully tapped by the age of 30.(一項令人驚奇的發(fā)現(xiàn)表明，我們的心智能力在30歲并沒有完全成熟。)

By the age of 21 he controlled the company.(他21歲就掌管了公司。)

By the age of sixteen he was the junior lightweight champion of Poland.(16歲時他已是波蘭少年輕量級冠軍。)

By the age of 40, 90% of men and women will have been married at least once.(40歲時，90%的男性和女性至少經歷了一次婚姻。)

Children ought to be able to read by the age of 7.(兒童7歲時應該識字了。)

If you can get kids by the age of 19, they don't start smoking hardly after that.(如果孩子們在19歲的時候就吸煙，他們從那以后很難不去吸煙。)

In some sports you're past it by the age of 25.(在某些運動中，人過25歲就難有作為了。)