a) is insufficient, b) is sufficient. Eligible numbers 2<n<100 are 4,9,16,25,36,49,64,81. 1 is not a prime number. 9,25,49,81 have only one prime factor each; 3,5,7,3 respectively. 4 only has one prime factor (2) as does 64 (8^2). The factors of 36 are 1,2,3,6,18. 2 and 3 are prime numbers. The answ...