Final answer:
The central idea of the article is that the scientific method is based on observations.
Step-by-step explanation:
The central idea of the article is that the scientific method is based on observations. The scientific method is a step-by-step process that scientists use to investigate and answer questions. It begins with making observations, which lead to the formulation of hypotheses, and then the testing of those hypotheses through experiments. Therefore, option d) The scientific method is based on observations is the correct statement