之前我們討論了：
下面討論其中的Zero Conditional
When we are thinking about facts which are generally true, we use:
當我們考慮事實時（這些事實大多數是真的），我們使用：
If + Present Simple一般現在時, Present Simple一般現在時
If you put water in the freezer, it becomes ice.
If you stand in the rain, you get wet.
If you heat ice, it melts.
You can see in the examples about the the condition always has the same result.
你可以在例子中看到這些條件經常會有相同的結果。
Notice how we use a comma after the first present simple tense clause.
注意我們如何在第一個一般現在時從句後使用逗號。
We can also reverse the order and use:
我們也可以顛倒順序：
Present Simple一般現在時 + If + Present Simple一般現在時
You get wet if you stand in the rain.
Ice melts if you heat it.
I can't sleep if I drink coffee at night.
Plants die if you don't water them.
Notice how the comma is not necessary with this word order.
注意這種單詞順序下，逗號就不是必須的了。