Answer:
The <u><em>second </em></u>line of defense.
Explanation:
In our bodies the <em><u>second line of defense</u></em> includes active immunity. It contains non-specific immune responses, but yet still contains specific responses for certain things such as inflammatory and fevers.
B. Covalent (Bond) I hope this helps! ^^
They release carbon dioxide into the atmosphere which in effect create green house gasses
A gateway substance is something that may be menial but could lead to something bigger, an example is weed in the drugs world, weed is not hard to get and is usually a gateway drug to stronger types of drugs and potentially more dangerous
