Averments in a pleading to which no responsive pleading is required or permitted shall be taken as denied or avoided. Averments in a pleading to which a responsive pleading is required are admitted when not denied in the responsive pleading, except that the following allegations must be proved.
(1) Those against a person under any disability;
(2) Those against executors or administrators;
(3) Those necessary to sustain an action for divorce or annulment;
(4) Those against persons whose names and residences are unknown, where there has been no attachment of property.
(5) Those against persons whose parental rights are sought to be terminated.