Which of the following are sources of low-level radiation? A) medical X-rays B) nuclear weapons testing C) buring of fossil fuels D) all of the above E) a and c only

The answer to this question would be E) a and c only

Nuclear weapon testing definitely gives a high-level radiation. Since the explosive power should be big, the amount of nuclear waste will also be big and it will give a high intensity of radiation. So option B and D will be out.

Medical X-ray will give low-level radiation. It will be much lower than CT-scan or any imaging method that using radiation. Burning fossil fuels also produce some radiation.