For each scenario below, answer yes if the life insurance policy would be included in the decedent's gross estate and no if it is not included in the gross estate:

a$.$ The beneficiary of the policy is the estate of the decedent.

b$.$ The decedent transferred the ownership of the policy to his daughter six years before his death but retained the right to change the beneficiary of the policy.

c$.$ The decedent transferred the ownership of the policy to his son six months before his death.

d$.$ The decedent transferred the ownership of the policy to his partner four years ago.