8. The following assets, which are not part of the probate estate, nevertheless are includible in the gross estate, except:

a. Property transferred to a revocable trust by the decedent 17 years prior to death

b. Property sold by the decedent two years prior to death for a private annuity of equal value

c. Property transferred to decedent's wife for life, then to their son if the son survives his mother, to the extent of the reversion

d. A life insurance policy transferred two and a half years ago on the decedent's life