Final answer:
An experiment is defined as an organized procedure conducted under controlled conditions where one variable is manipulated to observe the effect on another variable. This systematic process helps to validate scientific hypotheses.
Step-by-step explanation:
The correct definition of an experiment is A. An organized procedure under controlled conditions.
An experiment is a fundamental component of the scientific method. It is a method of conducting a scientific investigation under controlled conditions. During an experiment, researchers typically manipulate one variable (independent variable) to observe its effect on another variable (dependent variable). For instance, planting trees in different types of soil to observe growth rates is an experiment where the soil type is the independent variable and tree growth is the dependent variable. Controlling variables is essential to eliminate other factors that can affect the outcome, allowing the experimenter to make causal connections between what is manipulated and what is measured. The process is systematic and involves repetition to validate results and ensure reliability. Experiments may lead to a new understanding that can later be described in a scientific law, or necessitate a modification to an existing hypothesis.