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.