Is a + b = d?
I. The average of a, b and c is 6
II. The average of c and d is 9

A

If the statement I alone is sufficient to answer the question

B

If the statement II alone is sufficient to answer the question

C

If both the statements I and II are sufficient to answer the question but neither statement alone is not sufficient

D

If both the statements I and II together are not sufficient to answer the question and additional data is required