Need help figuring out the answers.. Hw would this work..?

I need yur help chegg!

3. Closure Prove or disprove the following claims: (a) The set of context-free languages over some fixed alphabet is closed under the operation of taking subsets (that is, if L1 is context-free and L2 C L1, then L2 is context-free.) (b) The set of context-free languages over some fixed alphabet is closed under Kleene star. e) The set of Turing-decidable languages over some fixed alphabet is closed under Kleene star. (d) Let A and B be sets of languages over some fixed alphabet , with AC B. If A is closed under some operation P, then B is also closed under P