S died in 2007 leaving property worth $ 500,000 in trust. The income was payable to X for life, remainder to Y. X and Y were both granted the unlimited right to invade the corpus for the benefit of X if they both agreed. Without ever exercising the right to draw upon the corpus, X died. How much, if any, of the trust corpus (still worth $ 500,000) is included in X's gross estate?

A. $ 0

B. $ 250,000

C. $ 500,000

D. None of the above