** Formal Languages And Automation Theory MCQs **

**Set V**

**Q1. Regular expression for all strings starts with ab and ends with ba is. **

**a)** aba*b*ba

**b)** ab(ab)*ba

**c)** ab (a+b)*ba ✔

**d)** All of the mentioned

**Answer is c)** ab (a+b)*ba **Explanation : ** The givem string ab (a+b)*ba starts with ab and ends with ba

**Q2. L is a regular Language if and only If the set of __________ classes of IL is finite.**

**a)** Equivalence ✔

**b)** Reflexive

**c)** Myhill

**d)** Nerode

**Answer is a)** Equivalence **Explanation : ** This is according to Myhill Nerode theorem, the corollary proves the given statement correct for equivalence classes.

**Q3. The generators of languages are ________________**

**a)** Regular expression

**b)** Grammars ✔

**c)** FSM

**d)** All

**Answer is b)** Grammars **Explanation : ** Grammars is usually thought of as a language generator. However, it can also sometimes be used as the basis for a "recognizer"—a function in computing that determines whether a given string belongs to the language or is grammatically incorrect.

**Q4. A language can be generated from simple primitive language in a simple way if and only if **

**a)** It is recognized by a device of infinite states

**b)** It takes no auxiliary memory ✔

**c)** Both are correct

**d)** Both are wrong

**Answer is b)** It takes no auxiliary memory **Explanation : ** A language is regular if and only if it can be accepted by a finite automaton. Secondly, It supports no concept of auxiliary memory as it loses the data as soon as the device is shut down.

**Q5. The regular expression of language which is starting and ending with different symbols is __________________
**

**a)** a(a+b)*b

**b)** b(a+b)*a

**c)** a(a+b)*b + b(a+b)*a ✔

**d)** All

**Answer is c)** a(a+b)*b + b(a+b)*a **Explanation : ** For explanation Join the discussion below

**Q6. Context Free Grammars has ________tuples**

**a)** 5

**b)** 4 ✔

**c)** 3

**d)** None

**Answer is b)** 4 **Explanation : ** Context free grammar G can be defined by four tuples as: G= (V, T, P, S)

**Q7. A grammar is said to be ambiguous grammar if it :-
**

**a)** produces more than one derivation tree

**b)** produces more than one left most derivation

**c)** produces more than one right most derivation

**d)** All ✔

**Answer is d)** All **Explanation : ** The grammear that satisfies all the mentioned options is ambitious

**Q8. Backtracking is allowed in **

**a)** NDFA

**b)** DFA ✔

**c)** Both a & b

**d)** None

**Answer is b)** DFA **Explanation : ** The transition from a state is to a single particular next state for each input symbol. Hence it is called deterministic which allows backtracking

**Q9. (a + b)(cd)*(a + b) denotes the following set **

**a)** {a(cd)nb|n = 1}

**b)** {a(cd)na|n = 1} ? {b(cd)nb/n = 1}

**c)** {a(cd)na|n = 0} ? {a(cd)nb/n = 0} ? {b(cd)na/n = 0} ? {b(cd)nb/n = 0} ✔

**d)** {acndnb|n = 1}

**Answer is c)** {a(cd)na|n = 0} ? {a(cd)nb/n = 0} ? {b(cd)na/n = 0} ? {b(cd)nb/n = 0} **Explanation : ** For explanation Join the discussion below

**Q10. Which of the following regular expression identity is true?
**

**a)** r(*) = r*

**b)** (r*s*)* = (r + s)* ✔

**c)** (r + s)* = r* + s*

**d)** r*s* = r* + s*

**Answer is b)** (r*s*)* = (r + s)* **Explanation : ** For explanation Join the discussion below

**Q11. R1 and R2 are regular sets. Which of the following is not true?
**

**a)** R1 and R2 need not be regular ✔

**b)** S* – R1 is regular

**c)** R1 ? R2 is regular

**d)** is regular

**Answer is a)** R1 and R2 need not be regular **Explanation : ** For explanation Join the discussion below

**Q12. Which of the following does not represents the given language?
Language: {0,01}
**

**a)** 0+01

**b)** {0} U {01}

**c)** {0} U {0}{1}

**d)** {0} ^ {01} ✔

**Answer is d)** {0} ^ {01} **Explanation : **The given option represents {0, 01} in different forms using set operations and Regular Expressions. The operator like ^, v, etc. are logical operation and they form invalid regular expressions when used.

**Q13. Recursive languages are
**

**a)** a proper superset of CFL

**b)** always recognized by PDA✔

**c)** are also called type 0 languages

**d)** always recognized by FSA

**Answer is a)** a proper superset of CFL**Explanation : ** For explanation Join the discussion below

**Q14. According to the given language, which among the following expressions does it corresponds to?
Language L={xÏµ{0,1}|x is of length 4 or less} **

**a)** (0+1+0+1+0+1+0+1)^4

**b)** (0+1)^4

**c)** (01)^4

**d)** (0+1+Îµ)^4 ✔

**Answer is d)** (0+1+Îµ)^4 **Explanation : ** The extended notation would be (0+1)4 but however, we may allow some or all the factors to be Îµ. Thus Îµ needs to be included in the given regular expression.

**Q15. Which of the following strings is not generated by the following grammar? S ? SaSbS|e**

**a)** aabb

**b)** abab

**c)** aababb

**d)** aaabb ✔

**Answer is d)** aaabb **Explanation : ** For explanation Join the discussion below

**If you have any doubts join the discussion below ,our Moderator will reply to your Queries**

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