A district may invest such surplus money, as its board deems wise or expedient in any of the following:
(a) Bonds issued by the district.
(b) Bonds issued by any school district any part of which is in a county containing any part of the county water district.
(c) Bonds issued by the State.
(d) Bonds issued by the United States.
(e) Registered warrants issued by the State.
(Added by Stats. 1949, Ch. 274.)