Like heroin, and cough syrup with codeine, can make a driver drowsy and unable to concentrate

This would be a correct conjecture. Codeine and Heroin while varying in potency (with Codeine being quite mild and Heroin being heavy), they are both a type of Opioid. Opioids are drugs derived from the active substance from Opium, which is used as a downer in both illicit and pharmaceutical drugs. Downer's are actually called depressants and are designed to depress the CNS (Central Nervous System), which does cause drowsiness if you were to take it all mildly. Two other depressants you may be aware of include Barbituates and Alcohol. 

There is tumerous cancer, kawaski disease and more.

(a) is not correct because one does not get increased cholesterol  from lifting weights.(b) is not correct because lifting weights cannot reduce the risk of a hereditary disease.(c) is not correct because back pain isn't a benefit! and plus, if he lifts weights properly, he should not have back pain.(d) is the correct answer because his ligaments will gain mass, making it easier for him to carry heavier weights and he will also be stronger!