English homework p.6急!!!!

If it's physical exercise like working out, "exercise" is uncountable, so "a lot of exercise" is right.

If it's something like homework that has lots of questions to answer or problems to solve, "exercise" is countable, so you say "a lot of exercises" is right.

That depends on how you regard it as. If they are verb form, they are both wrong. If they are noun form, a lot of exercise is correct because excercise is uncountable.

A lot of exercises.

Exercises are countable.