If ' a ' and ' b ' are positive integers. what is the value of ' a ' ?
I) b - a = 4
II) a + b = 2

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 the statements I and II together are sufficient to answer the question but neither statement alone is sufficient.

D

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