Identify the terms and the like terms in this expression.

7 + a – 2 + 3a + b^2

Which statements are true? Check all that apply.
a. The expression contains seven terms.
b. The terms in the expression are 7, a, 2, 3a, b2.
c. Constants are like terms.
d. 2 and b2 are like terms because they both contain the number 2.
e. a and 3a are like terms.
f. a, 3a, and b2 contain variables, so they are like terms.