Demarcus is a sole proprietor who had nonfarm net operating loss in 2020. Which of the following is NOT an option for his loss?

a) Demarcus may waive the carryback by attaching a statement to his timely filed 2020 return.

b) He may carry the loss back to his 2015 return using Form 1040-X.

c) He may carry the loss back to his 2015 return using Form 1045.

d) He may carry the loss back to his 2015 return using Form 1139.