Which statements about the factors of the terms in the expression 20 a + 15 a b + 24 b are true? Select three options. The factors common to 20a and 15ab are 1, 5, a, and b. The factors common to 20a and 15ab are 1, 5, and a. The factors common to 20a and 24b are 1, 2, and 4. The GCF of the expression is ab. The GCF of the expression is 1