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Which is a prime number?
A15
B17
C21
D27
Answer & Solution
Correct answer: B. 17
1. 15 = 3×5; 21 = 3×7; 27 = 3×9.
2. 17 has no factors other than 1 and 17.
3. Hence 17.
_Source: UGC NET Paper 1 Study Book (ugc-net.com class notes) — Number System_