you still need to show option c print if you filed taxes.. you do not get option c if you did not file tax ...in that case provide an explanation on separate sheet of paper for the reason why you do not have option c....
But option c is must if you filed taxes... you can files tax will 0 income.. if you are a student, you can explain that...
No minimum income is required for sponsoring only spouse but you need to prove that you ll be able to support both of you and you are not on any financial support ... option c will show that ...you can show your bank statement for financial proof...