一、名词做主语：
规律：不可数名词/单数名词做主语，系动词用is，复数名词做主语，系动词用are。
例：
Ice cream is delicious.
This book is good.
Lemons are sour.
二、人称代词做主语：
规律：
I am , We are
You are
He/She/It is , They are
例：
I am a teacher.
You are handsome.
He is young.
They are from China.
三、指示代词做主语：
规律：
This is , That is
These are , Those is
例：
That is funny.
These are some toys.
四、动名词做主语：
规律：系动词用is
例：
Lying is bad.
作业：
翻译：
1.狗是我们的好朋友。
Dogs are our good friend.
2.这个杯子很漂亮。
This cup is beautiful.
3.鱼很好吃。
The fish is very delicious.
4.我们是朋友。
We are friends.
5.你是一名医生。
You are a doctor.
6.她很友善。
She is very kind.
7.他们在超市。
They are at the supermarket.
8.这个很有趣。
This is funny.
9.看电视对眼睛不好。
Watching TV is bad for your eyes.
