美國的英文怎么寫大寫

　　In America, presidential elections are held every four years.

　　美國每四年舉行一次總統選舉。

　　Many Irish people went over to America during the famine.

　　許多愛爾蘭人在饑荒時期遷徙到美國。

　　South America separated from Africa 200 million years ago.

　　2億年前南美洲和非洲分離。

　　South America and Africa separated 200 million years ago.

　　南美洲和非洲于2億年前分離。

　　The proportion of small cars on America's roads is increasing.

　　美國公路上小汽車的比例在逐漸增加。