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ISRO2018-64

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A particular BNF definition for a "word is given by the following rules.

<word>      :: = <letter> I <letter> <charpair> I <letter> <intpair>
<charpair>  :: = <letter> <letter> I <charpair> <letter> <letter>
<intpair>   :: = <integer> <integer> I <intpair> <integer> <integer>
<letter>    :: = a I b I c I ......I Y I Z
<integer>   :: = 0 I 1 I 2 I ......I 9

Which of the following lexical entries can be derived from $\textsf{< word >}?$

  1. pick
  2. picks
  3. $\textsf{c44}$
  1. I, II and III
  2. I and II only
  3. I and III only
  4. II and III only
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3 Answers

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pick can't be generated other are generated hence ans should be B
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Ans: D.

What I thought, "word" is having only 4 char. Which can't be derived from the grammar.

"words" is having 5 char, which is odd, so can be derived from the grammar.

Also c22 can be drived.

So ans is II and III, implies option D.
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