选B.
homework是不可数名词,所以用lots of.
你说的这些词的区别不完全正确,
many是修饰可数名词复数,如many students
lots of=a lot of 既修饰可数名词复数也可修饰不可数名词 如：a lot of money,a lot of books
a lot是修饰动词,
little是修饰不可数名词 如：little money
ihomework是不可数名词,可以说so much homework,lots of homework