Final answer:
The first step in the scientific method when addressing a question about a natural phenomenon is to formulate a hypothesis, which is a testable tentative explanation.
Step-by-step explanation:
According to the scientific method, the first step scientists should take when they have a question about a natural phenomenon is to formulate a hypothesis. A hypothesis is a tentative explanation for an observation, or a set of observations, that can be tested through experimentation. In the context of the scientific method, this comes after an initial observation and before conducting experiments or collecting data. A well-crafted hypothesis provides a foundation for setting up an experiment and is an essential part of the scientific inquiry process.