(a) A district may require that monuments or markers shall be placed at interment plots.
(b) A district may adopt minimum requirements for the permanency of monuments or markers.
(c) A district may cause to be purchased and placed suitable permanent monuments or markers at the interment plots of indigents, persons whose estates are insufficient to pay for the monuments or markers, or persons who have no responsible survivors to pay for the monuments or markers. A district may accept gifts or donations for the exclusive purpose of purchasing and placing these monuments or markers.
(d) A district, a member of the board of trustees, a district officer, or a district employee shall not engage in the business of selling monuments or markers.