GATE | GATE CS Mock 2018 | Question 23

Consider the following grammars
(S1) :

A --> aBCD
B --> bc|c
C --> d|∈
D -> b

(S2) :

A --> aBCD
B --> bc|∈
C --> d|c
D -> b

(S3) :

A --> aBCD
B --> bc|∈
C --> d|∈
D -> b

(S4) :

A --> aBCD
B --> bc|c
C --> d|c
D -> b

Which of the following grammar has same follow set for variable B?
(A) Only (S1), (S2) and (S3), (S4)
(B) Only (S1), (S3) and (S2), (S4)
(C) Only (S2), (S3) and (S1), (S4)
(D) None of the above

Answer: (B)
Explanation: Grammar (S1) and (S3) has follow sets :

A = {$},
B = {b, d},
C = {b},
D = {$}

Grammar (S2) and (S4) has follow sets :

A = {$},
B = {c, d},
C = {b},
D = {$}

So, option (B) is correct.
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