(a) An irrevocable transfer of property from A to B in trust for the beneficial use of C will ordinarily constitute a gift from A to C. Subsequent transfers or additions to the trust corpus by A will likewise ordinarily constitute gifts from A to C.

(b) A transfer of property from A to B in trust for the beneficial use of A does not constitute a gift. However, the payment of the income from the property to a person other than A constitutes a gift.

(c) A transfer of property from A to B in trust for the beneficial use of A during his life, upon the termination of which the property is to go to C, constitutes a gift of a remainder to C.

(d) A transfer of property from A to B in trust for the beneficial use of C does not constitute a gift if A reserves the power either to designate a new beneficiary other than himself, or to modify or alter the disposition in any way not beneficial to himself, even though he may in all other respects have surrendered his dominion and control over the property. A gift will occur, however, if A should relinquish the power during his lifetime.

(e) A transfer of property from A to B in trust for the beneficial use of C without reservation, except to the extent that if C should predecease A the property will revert to the latter, constitutes a gift from A to C. The tax in such case is computed as though the transfer were made subject to a contingency or condition (see Section 15210).