If GCD(a,b)=5\text{GCD}(a, b) = 5GCD(a,b)=5, which of the following is definitely true about aaa and bbb?
aaa and bbb are both multiples of 5
aaa and bbb are both prime numbers
The sum a+ba+ba+b is a multiple of 10
The difference a−ba-ba−b is 5