Plug in numbers here.
For statement 1, let's say that c=2 and d=2. These are acceptable numbers, since the make c(d+1)=2(2+1)=6, which is even. And for these numbers, c is even.
But you could also have c=1 and d=1, since 1(1+1)=2, which is even, so those values satisfy the statement. (When you're plugging in on Yes/No data sufficiency, the most important thing is to satisfy the statement.) And here, c is not even, so the statement is insufficient.
Similar deal for statment 2--in fact, you can use the same values. So 2 is insufficient.
And when we look at them together, again, both sets of values work in both statements, so together they're insufficient. So the answer is E.
Matt McIver
Princeton Review Instructor