GATE | GATE CS 2012 | Question 28
What is the minimal form of the Karnaugh map shown below? Assume that X denotes a don’t care term.
(A) b’d’
(B) b’d’ + b’c’
(C) b’d’ + a’b’c’d’
(D) b’d’ + b’c’ + c’d’
Answer: (B)
Explanation: There are two prime implicants in the following K-Map-
Prime Implicant higlighted in Green = 
Prime Implicant higlighted in Orange = 
So the Boolean expression is- 
Therefore option (B) is correct.
This explanation is provided by Chirag Manwani.
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