How do the effects of ketamine vary at different dose levels?
a) Low doses produce analgesia, moderate doses produce sedation, high doses produce dissociative anesthesia
b) Low doses produce sedation, moderate doses produce hallucinations, high doses produce respiratory depression
c) Low doses produce euphoria, moderate doses produce delirium, high doses produce agitation
d) Low doses produce hypotension, moderate doses produce tachycardia, high doses produce cardiac arrest