a lot of=lots of, 所以下面的句子都是正确的：
- My cousin eats a lot of food when he’s nervous.
- Don’t you hate it when we have lots of homework?
- Lots of people mourned the sudden passing of James Hellwig, aka the Ultimate Warrior.
但是a lot of和lots of并不够正式，正式场合应该用many, a large number of等类似的词语。