What is the minimum dose that results in reddening of the skin?

What is hydroelectric power produced by?

Loss of protected health information collected for research should be directly reported to:

Why is the theory of evolution important? it disproves all other theories about how life began. it provides a topic for debate. it is a unifying concept in biology. it explains how life began. i know for sure, it is not "it is a unifying concept in biology."