Answer:
C. 2 · 2 · 2 · 2
Explanation:
Prime numbers are natural numbers greater than 1 that are not a product of two smaller natural numbers.
Answers B and D do not have a product of 16, so they are eliminated. Answer A does have a product of 16, however, 4 is not a prime number and can be split up into 2 · 2.
Therefore, Answer C is correct.