The most accurate answer would be: By testing their hypotheses.
In scientific fields, knowledge and understanding are primarily gained through the formulation and testing of hypotheses. This process involves experimentation, observation, and the gathering of evidence, which allows scientists to confirm or refute their initial ideas and develop a deeper understanding of the subject matter. While consulting with experts and using the latest technology can support this process, it is the hypothesis testing that is central to scientific inquiry. Making value judgments is not a fundamental method of gaining scientific knowledge.