Which of these is an example of a compound sentence?

a.
Fish is a great source of Omega 3 fatty acids.
c.
Lance Armstrong keeps saying he’s going to retire, yet each year he decides he’s not quite finished after all.
b.
It took Shelley three hours to finish getting ready for the show.
d.
all of these

Please select the best answer from the choices provided

A
B
C
D