Designing shoes is hard work. it will pay off in the

identify the sentence that correctly combines the above passage into a compound sentence.

a.) because designing shoes is hard work, it will pay off in the end.
b.) although designing shoes is hard work, it will pay off in the end.
c.) designing shoes is hard work; but it will pay off in the end.
d.) designing shoes is hard work; however, it will pay off in the end.