Can be harmful to our health and lead to problems such as
depression if we don’t learn to handle it properly.

Conflict can be harmful to our health and lead to problems such as depression if we don't learn to handle it properly.

Hope this helps :)

(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!