Question

Identify the correct sentence.
a.no. you​ can't be​ serious;
b.​no! you​ can't be​ serious!
c.​no, you​ can't be serious.
d.​no, you​ can't be​ serious?

Answer 1

I think it is probably c, although none of the these is correct.  Capital letters are an essential part of any sentence.