The correct answers are: “B) It shows Hamlet’s indecision. D) It shows Hamlet’s confusion. E) It shows Hamlet’s idleness.”
Indeed, this self-deprecatory monologue is an instance of Hamlet criticizing what he perceives as his indecision (the adjective “dull” is very explicit in that regard), his confusion (the adjective “muddy-metled” conveys this perfectly) and his idleness (“And can say nothing; no”).
The source of his moral distress is what he perceives as his own inaction in finding out whether King Claudius actually poisoned King Hamlet or not and his delay in exacting revenge upon him if such is the case. Hamlet is conscious that his thoughts are not only occupied with his thirst for revenge and justice but with many other issues that affect him to the point of being inactive.