Ans : B
By decision property of cfg
1.does L(G) is empty (Decidable)
2.does L(G) is finite(Decidable)
3.does L(G) is regular(Undecidable)
4.does w belong L(G) is or not (Decidable)
5.does G is Ambigeous(Undecidable)
6.equality of cfg is Undecidable
7.compliment of cfl is undecidable
8.intersection of two cfl is undecidable
9.sigma star is also decidable