Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[Q]: Question: When volume does not change, temperature is proportional to what other property? Answer: pressure
[A]: Pressure and temperature at constant volume are directly proportional.

[Q]: Question: What remains a constant of radioactive substance over time? Answer: rate of decay
[A]: The rate of decay of a radioactive substance is constant over time.

[Q]: Question: What is a three dimensional snycline? Answer: a basin
[A]:
In a syncline, rocks arch downward. A three-dimensional syncline is a basin.