B transfers property to T in an irrevocable trust, life estate to D, remainder to X. Under the terms of the trust D is entitled to require T to pay him any of the trust corpus that D needs for his support or comfort. D dies without ever exercising the power. Would the corpus be included in D's gross estate?

A. No, because D holds a special power of appointment

B. No, because D's power is limited by an ascertainable standard

C. No, because D never exercised the power of appointment

D. Yes, because D holds a general power of appointment