The answer is false the don’t always work in pairs
Hemoglobin, Keratin, Collegen, Actin, and Elastin are different kinds.
the answer choice would be D
here is why because within those 60 mins you can do a mix of different activities. You can even decide to do strength training for 30 mins and then do resistance training for 30 mins. This means you would get in your full training of 60 mins but would have the ability to do two different categories of training during 60 mins. you would knock out two different exercises within 60 mins. doing the same thing for 60 mins could get boring so you have the chance to move on to something else for the other 30 mins.
hope this helps and makes sense