Given a scientific passage and an answer, generate a question for the given answer.

Passage: In science, a theory has been repeatedly shown to be true. A theory is supported by many observations. However, a theory may be disproved if conflicting data is discovered. Many important theories have been shown to be true by many observations and experiments and are extremely unlikely to be disproved. These include the theory of plate tectonics and the theory of evolution. Answer: many observations
What does a theory need to be supported by?