Nova DS

[60sec]

Is CAB a code word in language Q?
1) ABC is the base word
2) If C immediately follows B, then C can be moved to the front of the code
word to generate another word

Official Answer

SPOILER: C

Explanation

SPOILER: From (1), we can't determine whether CAB is a code word since (1) give no rule for generating another word from the base word. This eliminates A and D.
Turning to (2), we still can't determine whether CAB is a code word since now we have no word to apply this rule to. This eliminates B.
However, if we consider (1) and (2) together, then we can determine whether CAB is a code word:
From (1), ABC is a base word
From (2), the C in the code word ABC can be moved to the front of the word: CAB
Hence, CAB is a code word and the answer is C.

I don't think ETS asks these kind of questions.

[karmaholic]

Lol! This is more like generating a elements from a grammar! Finite Automata!

I dont think ETS would ever come up with something like this.. atleast I've never seen a question like this.. I'll keep my fingers crossed!