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Which set is FINITE?
A{x ∈ ℕ : x is odd}
B{x ∈ ℕ : 2x − 1 = 0}
C{x ∈ ℕ : (x − 1)(x − 2) = 0}
D{x ∈ ℕ : x is prime}
Answer & Solution
Correct answer: C. {x ∈ ℕ : (x − 1)(x − 2) = 0}
Option A = {1, 2} — finite. Option B = ∅ (2x − 1 = 0 → x = 1/2, not a natural number); ∅ is finite too. But the standard answer treats option A as the unambiguous finite NON-EMPTY set. Option C (primes) and D (odd naturals) are infinite. (Strictly both A and B are finite — typical NCERT exercise emphasises A as 'finite' since B = ∅ counts as 'empty/finite'; in the choice list above A is the unambiguous answer for 'finite non-empty'.)
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