Question

Select the sentence that is written correctly.

A. This is a low-intensity workout.
B. This is a low intensity workout.
C. This is a low, intensity workout.
D. This is a low intensity work-out.

Answer 1

B. 
This is a low intensity workout 

Because you dont need any type of punctuation in this sentence  

Answer 2

I would say B. because you don't  really need a hyphen.