In which of the following situations would trust income be taxed to the grantor and the trust assets be included in the grantors gross estate?

a revocable trust that paid all income to the grantor and that the grantor made irrevocable within three years of his death

an irrevocable trust in which the grantor has no retained interest and that pays all income to the grantors spouse

an irrevocable trust in which the grantor retained a reversionary right, the value of which was greater than 5% of the value of the trust assets both at the time the trust was created and at the grantors death

an irrevocable trust in which the grantor was the trustee, and the trustee had discretion over the distribution of income

I and II only

II and III only

III and IV only

I, III, and IV only