The covering on electric plugs and around wires is made of an what?

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Darwin’s hypothesis about how life changes over time is now called?

Fossils of ancestors of the modern horses show a small 4-toed almost dog-like browsing animal named eohippus over time the horses got larger lost toes and changed to a grazing diet what is the best explanation of why this change occurred