ISRO2011-68

Question

Which of the following sentences can be generated by 

S -> aS $\mid$ bA

A -> d $\mid$ cA

• A. bccdd
• B. abbcca
• C. abcabc
• D. abcd

Answer 1

S=>aS

=>abA

=>abcA

=>abcd

Hence,Option(D) abcd is the correct choice.

Answer 2

Option A-- two consecutive d can't generate

Option B&C can't generate bcz ..any string must endup with d to get accepted by this grammar.

Option D is correct bcz

S->aS

  -> abA

 -> abcA

-> abcd

Answer 3

option D

in any case d would come at end, that eliminate option B,C

d cannot come twice, that eliminate option A

so option D is the winner

Answer 4

ans is (d)