The board, after the hearing of any exclusion petition, shall order the exclusion of all or any part of the land described in it when as to the land to be excluded either:
(a) The board judges that the land will not be benefited by the operations of the district.
(b) The board deems the exclusion to be for the best interests of the district and one of the following is true:
(1) No interested person has filed objections in writing showing cause why the land should not be excluded.
(2) All written objections made to the exclusion have been withdrawn.
(3) No written objection made to the exclusion is sustained at the hearing.
(Amended by Stats. 1963, Ch. 1607.)