Final answer:
Gertrude shows loyalty to Hamlet by telling Claudius that Hamlet is truly mad.
Step-by-step explanation:
In her response to Claudius after Hamlet kills Polonius, Gertrude demonstrates some loyalty to Hamlet by telling Claudius that Hamlet is truly mad. This response implies that she is trying to protect Hamlet by suggesting that his actions are a result of his madness rather than a deliberate choice. By attributing his behavior to madness, Gertrude is offering an explanation that may help mitigate the consequences for Hamlet.