Actions for divorce from the bonds of matrimony or for separate support and maintenance must be tried in the county (a) in which the defendant resides at the time of the commencement of the action, (b) in which the plaintiff resides if the defendant is a nonresident or after due diligence cannot be found, or (c) in which the parties last resided together as husband and wife unless the plaintiff is a nonresident, in which case it must be brought in the county in which the defendant resides.