Explanation

This question gives three equations. The number of variables is four--a through d--so we appear to be short one equation in order to solve for all variables, including c. But there may be simpler ways to get c. For example, from the last equation, if we can get d, we will have c. My eyes skip down and boom, there is the value of d in the second statement. So, Statement (2) is sufficient. As for Statement (1), we have the value of a. We look to see where we can apply that: in the first equation, we can determine c from a. So Statement (1) is also sufficient.

The correct answer is (D).