The statement that is true about theories is:
(c) They are formulated after several repeated investigations produce the same or similar conclusions.
Theories in science are developed after multiple experiments and investigations have been conducted and consistently produce the same or similar results. Theories are scientific explanations or models that are well-supported by empirical evidence and have withstood rigorous testing and scrutiny. They are not formulated before experiments begin or during a single investigation with groundbreaking results but rather after a body of evidence has been accumulated over time.