(a) Bonds secured wholly or in part by a pledge of the revenues of the district may be secured by all or that part of the revenues specified in the resolution authorizing the bonds or in the indenture securing the bonds.
(b) In making any pledge of the revenues, the right under the conditions specified to issue additional bonds which will be on a parity with, senior to, or subordinate to the bonds then being issued, may be expressly reserved.
(c) Within the discretion of the governing body, bonds may be secured further by a lien on all or any part of the physical property of the district.