Question

Please also note that there might be multiple answers for each question.

Q1: Which of the following claims are true?* 1 point The recognizable languages are closed under union and intersection The decidable languages are closed under union and intersection The class of undecidable languages contains the class of recognizable languages For every language A, at least one of A or A*c is recognizable Other: This is a required question Q2: Which of the following languages are recognizable? (Select all that apply)* 1 point E-DFA-( 1 A is a DFA and L(A) is empty) ALL DFAAI A is a DFA over Sigma and L(A) Sigma) The complement of EDFA | | E-TM = { 1 M is a TM and L(M) is empty) The complement of E_TM Other: Q3: Select all the true statements below. * 1 point If a language L and complement of L are both recognizable, then they are both decidable A TM is undecidable but not Turing recognizable ATM is undecidable and Turing recognizable The complement of A TM is Turing recognizable Q4: What can you conclude from knowing that A TM reduces to a language L? (Select all that apply)* 1 point L is empty L is decidable L is undecidable L is infinite Q5: Assume that a language A is reducible to language B. Which of the following claims are true?* 1 point A decider for language A can be used to decide the language B. If A is decidable then B is decidable too. If A is undecidable then B is undecidable too.

Answer 1

Q 5

Answer

if A is undecidable then B is undecidable too

Explanation

Lets take the first statement

A decider for language A can be used to decide the language B

It is wrong

the correct one should be

a decider for language B can be used to decide the
language A

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Next statement

If A is decidable then B is decidable too

This is also wrong

for e.g if A is the empty language and B is A, surely it is reducible to A, but It is undecidable

the correct one is

If B is decidable then A is decidable too

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If A is undecidable then B is undecidable too

This is correct one

so answer is C

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all the best