If the 2010 study of children in western canada is accurate, parents need to worry more about their children's exposure to than their exposure to

To complete the given sentence or statement the first and second answer will be the parents need to worry more about their children's exposure to wood smoke than their exposure to carbon monoxide, if the 2010 study of children in western Canada is accurate.

The one that most represents the earths mantle would be the skin since the mantle is the upper part of the earths depths which is just like the skin of an apple.