Solution

The correct answer is option1

Key Points

• Context-free language is closed under Union, Concatenation, and Kleen closure. But not closed under complementation and intersection.
• If a Language is Context Free, it can be either deterministic or non-deterministic language. only deterministic languages are accepted by the deterministic pushdown automaton.
• Let L1 and L2 be Context-free language

Option 1: 

L1 ∪ L2 is context-free

As context-free languages are closed under union. So it is correct