(

a) A member upon application for a disability retirement pursuant to

Chapter 26 (commencing with

Section 24100), may elect, as provided in

Section or 24300.1 to receive an actuarially modified disability retirement allowance. (

b) For purposes of this section, the member shall either elect to receive an unmodified allowance or designate an option beneficiary on a properly executed form prescribed by the system, either of which shall be filed with the system on or before the last day of the month in which the member’s disability retirement is approved by the system. The option shall become effective on the effective date of the disability retirement allowance.

The modification of the disability retirement allowance under the option elected shall be based on the ages of the retired member and the designated option beneficiary as of the effective date of the disability retirement. The modification shall be applicable only to the disability retirement allowance payable pursuant to subdivision (

a) of

Section 24106. (

c) Except as provided in Sections 24300, 24300.1, 24320, 24321, 24322, and 24323, a member may revoke or change an election of an option no later than days from the date of the member’s initial disability retirement benefit payment. (

d) If a member dies prior to electing an unmodified allowance or an option, the death benefits shall be payable under

Chapter 23 (commencing with

Section 23850), regardless of whether the disability retirement application is or would have been approved.