Hi nedd help with selelcting slipcovers for sofa?

Question:Hello everyone,
We are planning to buy slipcovers for oursofa and loveseat.the problem the cushions in our sofa always come s away from the sofa. so which one of the following type slipcovers will help to resolve the issue..
1)stretch
2)two piece stretch

Please do give me a reply ASAP.Thank you all in advance.

Answers:
Ya think maybe home maintenance and repairs is the best place to ask a stupid question like this? I agree you need help, but it ain't got nothing to do with "selelcting" anything.