For this problem, you will need to be comfortable with how odds and evens interact when added and multiplied.
(1)
Assume c is even, then this statement holds true if d is even or odd: 2*(2+1) = 6 Even
Assume c is odd, then this statement holds true if d is odd: 3*(3+1) = 12 Even
Insufficient, since c can be either even or odd.
(2)
Assume c is even, then this statement holds true if d is even or odd: (2+2)(1+4) = 20 Even
Assume c is odd, then this statement holds true if d is even: (1+2)(2+4) = 18 Even
Insufficient, since c can be either even or odd.
Together
Assume c is even, then these two statements hold true if d is even or odd:
2*(2+1) = 6 Even
(2+2)(1+4) = 20 Even
Assume c is odd, then
(1) is true only if d is odd, but not even
3*(3+1) = 12 Even
3*(3+2) = 15 Odd
(2) is true only if d is even, but not odd
(1+2)(2+4) = 18 Even
(1+2)(2+3) = 15 Odd
Since d cannot be both even and odd at the same time, this case does not work and c cannot be odd. Only the first case works so c must be even. Sufficient.
