Explanation

Factor 26381 by trial division: 26381 ÷ 23 = 1147, and 1147 = 31 × 37. Since 23, 31 and 37 are all prime, the prime factorisation is 26381 = 23 × 31 × 37 with no repeated factors. The distinct prime factors are therefore 23, 31 and 37. This matches option (d).