Final answer:
To determine why a car won't start, first check the battery by trying to turn on the headlights. This is the first step in applying the scientific method to troubleshoot the issue.
Step-by-step explanation:
When your car does not turn over and nothing else happens, the first action to take in determining the cause of the problem is to check the battery. In this situation, you should choose option (3): Turn on the lights to check the electrical flow from the battery. This initial check can help you determine if the battery has any charge; if the lights do not turn on, it is likely that the battery is dead or disconnected. If the lights do work, the problem could be related to other components such as the starter or the electrical system.
Apply the scientific method to troubleshoot the issue; begin with a hypothesis that the problem might be in the battery, then test this hypothesis by turning on the headlights to check for electrical power. If the hypothesis is incorrect, a new one should be stated and tested until the root cause of the problem is found.