1.两者都是做原因状语的.表示道歉的理由.
2.条件状语从句 原句应该是
if we unit,we will stand.if we divide ,we will fall.
3.It 主语 took 谓语 a long time for （the connection between body temperature and illness ）宾语 （to be made）宾补
固定句型 it takes some time to do 某事要花费···时间
4.入口处的玻璃门代替了木门,这样在白天可以让自然光进入室内.
letting in the natural light during the day伴随状语
take the place of 代替···
at the entrance 在入口处