Regular languages and finite automata

Question 151

Let L1 be regular language, L2 be a deterministic context free language and L3 a recursively enumerable language, but not recursive. Which one of the following statements is false?

• L3 ∩ L1 is recursive
• L1 ∩ L2 ∩ L3 is recursively enumerable
• L1 ∪ L2 is context free
• L1 ∩ L2 is context free

Question 152

Which one of the following is FALSE?

• There is a unique minimal DFA for every regular language

• Every NFA can be converted to an equivalent PDA

• Complement of every context-free language is recursive

• Every non-deterministic PDA can be converted to an equivalent deterministic PDA

Question 153

Match the following:

• (1)
• (2)
• (3)
• (4)

Question 154

Which one of the following regular expressions correctly represents the language of the finite automaton given below

• ab*bab* + ba*aba*

• (ab*b)*ab* + (ba*a)*ba*

• (ab*b+ba*a)*(a*+b*)

• (ba*a+ ab*b)* (ab* + ba*)