Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Ex Input:
When the smooth muscle relaxes, the arterioles dilate, allowing blood to enter the capillaries.

Ex Output:
When the smooth muscle relaxes, the arterioles dilate, allowing blood to enter the what?


Ex Input:
Carbon 14 isotope of carbon is typically used to date ancient items.

Ex Output:
What isotope of carbon is typically used to date ancient items?


Ex Input:
Animals can transport the waste material known as urea in the circulatory system and store it safely at high concentrations.

Ex Output:

Animals can transport what waste material in the circulatory system and store it safely at high concentrations?