引导条件状语从句的连词(重点)：
1)条件状语从句主要由if, unless, supposing(suppose)引导：
if: If it rains tomorrow , we will have to stay at home.
unless: I won't write unless he writes first. 我不写信，除非他先给我写。
2)条件状语从句还有其他形式：(难点)
You will always have a home as long as I have anything.
只要我有家产，你就永远会有一个家。