Which set is empty?
A{x : x ∈ ℝ, x² = 4}
B{x : x ∈ ℕ, x < 1}
C{x : x ∈ ℕ, x² = 4}
D{0}
Answer & Solution
Correct answer: B. {x : x ∈ ℕ, x < 1}
Natural numbers start at 1 (NCERT convention) or 0; either way, no natural number is < 1 strictly, so this set is empty.
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