as many students got preparatory sc rank. so can I fill both nit and iit in registration form. so that if I don't get iit for preparatory course. I go for nit
Yes of course you can fill NITs. You can fill both IITs and NITs as well as IIITs and GFTIs also. But you need to check the cutoff rank and your obtained rank and to make an idea whether you can get chance or not. Allotment of the colleges are done on the basis of choices you fill and your rank.
Hope you get my point. All the best.