The correct option is C Stainless steel
Let's break this down.
Plastic - first of all, it is not a solution of any kind. It is a single molecule repeated throughout, which is called a polymer. But if you have ever heard about plasticizers in plastic, they together form a solid-solid solution.
Kevlar - It is also a polymer
Stainless steel - You must be thinking it is an alloy. Voila! All alloys are solutions. They are homogeneous, single phase.
Gulab Jamun - Very yummy! But just a mixture.