All of these are related to the formation of oil or natural gas except - a) decomposed animals b) decayed plants eliminate c) sedimentary rocks d) active volcanoes

I think that the answer is sedimentary rocks

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.