Final answer:
The data of Huey and colleagues (1989) on thermoregulation in garter snakes is an example of the observational method used by evolutionary biologists to test hypotheses about adaptations. Therefore, the correct option is 3,.
Step-by-step explanation:
This method involves observing and recording the behavior or characteristics of organisms in their natural habitats without manipulating any variables. The data of Huey and colleagues (1989) on thermoregulation in garter snakes is an example of the observational method evolutionary biologists use to test hypotheses about adaptations. In the case of the garter snakes, the researchers observed how the snakes regulated their body temperature in different environmental conditions.