Answer:
D
Step-by-step explanation:
3,11,23, and 31 can only be divided by 1 without becoming a decimal.
6
Factors of 90 are: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
Factores of 42 are: 1, 2, 3, 6, 7, 14, 21, 42
6 is the greatest common factor.