Which of these sentences uses correct punctuation?

a. francis had a lot on his mind that afternoon, he was concerned about his mother’s illness and about losing his job.
b. the packing instructions asked each camper to bring the following items; a flashlight, a sleeping bag, sunscreen, and a book for independent reading.
c. in time, of course, all issues get resolved, but not necessarily in the way you would like.
d. the king ordered that all his subjects should show their allegiance through common forms of attire: yet many people continue to wear the traditional hats of their various regions.