O2 (oxygen) is a covalent compound
If a portion of the grass was destroyed by wildfire, then the population of bison that feed on the grass will decrease. This is because there would be very little grass left for them to eat, and they don't eat anything else.
I am pretty sure it is <span>D. Microbiologist</span>
Viruses are not always classified as living cells because they cannot live independently. They rely on a host to provide all resources to live, without a host they are in a dormant, near dead like state. Therefore it has to define a virus as dead or alive as it may or may not have a host.