以balloons have been used for sport for aboutone hundredyears.开头的文章
问题描述：
以balloons have been used for sport for aboutone hundredyears.开头的文章
答
Balloons Balloons have been used for sport for about one hundredyears.There are two kinds of sport balloons,gas and hot-air.Hot-air balloons are safer than gas balloons,which may catch fire.Hot-air ba...