Don says he is a non-smoker. Suggest one other way carbon monoxide could have got into Don's blood before he came to work that day.

Aand b would both be correct

Probably because you wake up early. even when i get a good nights sleep i still feel tired if i wake up early. or maybe you just need coffee.

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.