The answer is cotton. It is natural because it is grown and easily woven in to clothes :)
heightened temperatures can cause enzymes to work more quickly whereas if the temperature gets too high the enzyme stops working, If the temperature around an enzyme gets too high, the enzyme loses its shape, which is known as denaturation, and will eventually stop working
The term organic, as related to compounds, would be best defined as a compound that contains chain of carbon and hydrogen atoms which are bonded covalently. Common other atoms that could be included are hydrogen, nitrogen and oxygen.