Step-by-step explanation:
(72)¹⁴³ ≡ x (mod 7)
Since 72 ≡ 2 (mod 7),
72³ ≡ 2³ (mod 7) ≡ 1 (mod 7).
Therefore (72)¹⁴³ = (72³)⁴⁷ * (72²)
≡ 1⁴⁷ * 4 (mod 7) ≡ 4 (mod 7).
The answer is A.
