this comes from Thrasymachus
in the following
Καὶ εἶδον τά̄ς τε Δαναΐδας μέγαν κρᾱτῆρα ὕδατος πληροῦν μάτην πειρωμένᾱς
why is πληροῦν singular and Δαναΐδας plural since πληροῦν seems to modify Δαναΐδας
First off, is this the normal thing for Ancient authors to do. Second, would putting πληροῦν in the plural be correct. Third, is there some condition under which the singular is preferred over the plural.