This answer is unsupported. Saying that regular afternoon exercise is “required” for adequate deep-sleep is too strong. We only know from the stimulus that afternoon exercise can increase deep-sleep.

This answer is unsupported. The Researcher’s study is limited to exercise performed in the afternoon. We don’t know from these results what effects morning exercise could cause, if any.

This answer is unsupported. We don’t know from the stimulus whether a slight increase in a person’s body temperature is the “best way” to get increased deep-sleep. There could exist many other methods for this same effect.

This answer is unsupported. It could be true that one or two people in the control group experienced a rise in body temperature, but that doesn’t change the 33 percent increase in deep sleep for the group that exercised.

This answer is strongly supported. The Researcher hypothesizes that the rise in body temperature is the cause of increased deep-sleep for the people in the study. Exercise is one method for achieving this effect, but there are likely to be others.