The office of an elected officer of the City shall become vacant upon his death or resignation, or upon his recall, pursuant to Section 2 of Article III of this Charter, and may, upon complaint and hearing, be declared vacant by resolution of the Council, if: (a) he shall not be a registered elector of the City; (b) he shall not reside int he City, or shall not have resided in the City continuously for a period of at least one year immediately preceding his election; or, in the case of a Ward Councilman, he shall not reside in his ward or shall not have resided therein continuously for a period of at least the one year immediately preceding his election; (c) he shall hold any incompatible public office; or (d) he shall have any material financial interest in any contract to which the City is a party.