Good Portrait lens for Canon 7d?

Im in the processes of buying a new lens but im so conflicted right now. Im not sure if i should get the 24- 70mm f2.8 or 24-105 f4 or go with prime and go with the 135mm F2 or 100 F2.8 these are the lenses in my budget right now but i do like the versatility of the zoom lenses.