At the conclusion of the hearing, the board may either:
(a) Adopt the report.
(b) Modify the report.
(c) Cause a new report to be made to be again set for hearing as in the first instance.
(d) Abandon, either in whole or in part, the levying of any assessment pursuant to the report.
(e) Determine that the assessment is necessary and make an order of supplementary assessment.