Find the prime factors of 28. A. 2, 4, 7 B. 2, 7 C. 4, 7 D. 1, 2, 4, 7 and 28

The prime factors are the prime numbers used in the division.
The prime factors of 28 are 2 and 7.

Comparing this with the given options:
A. 2, 4, 7 (4 is not a prime number)
B. 2, 7 (Both 2 and 7 are prime numbers)
C. 4, 7 (4 is not a prime number)
D. 1, 2, 4, 7 and 28 (1, 4, and 28 are not prime numbers)

The correct option is B.

The final answer is $\boxed{\text{B. 2, 7}}$.