Final answer:
Arthur Jensen concluded that both genetics and environment contribute to IQ, with Level II intelligence showing differences among ethnic groups.
Step-by-step explanation:
Arthur Jensen's conclusions regarding IQ were that both genetics and environment contribute to IQ. He believed that intelligence is determined by genetics, with Level I abilities remaining consistent among the human race. However, he also found that Level II intelligence exhibited differences among ethnic groups. It is important to note that Jensen's conclusions were highly controversial and sparked debate regarding race and intelligence.