Answer:
In the second and third paragraphs, the author develops her claim by citing scientific evidence.
She references a study that found that during the summer months, people tend to have higher levels of melatonin, a hormone associated with sleepiness and fatigue.
She also cites research that suggests that people tend to be less active during the summer because of the warmer temperatures.
Finally, she notes that the summer months are associated with an increase in cravings for sugary, fatty foods, which can lead to weight gain and a lack of energy.
By providing scientific evidence to back up her claim, the author is able to demonstrate why summer might make us feel lazy.