Medium level - negative integers

[Brent@GMATPrepNow]

Please note that this is not an official GMAT question; it’s my attempt to create mid-range (500 to 650-level) GMAT-style questions for this forum.

[truplayer256]

I would go with C. Two negative numbers added together produce a number that's less than zero. Since ab+cdef<0, we can assume that either a or b is negative and that three of the letters in cdef are negative, since a negative cubed is always negative.

[Brent@GMATPrepNow]

Actually, the answer is D (although I think that many will choose C)
Here's my solution: