I think the question can be rephrased like this: which of the following forms are forms of "to be", which is a linking verb.
and the answer is B:
all in present:
am - first person singular
is- third person singular
are - plural
and the forth form:
was - simple past
It could be anything based off of where you live. for example, if you live in a forested area (montana, washington, etc) it would probably be green because that color is the most common and it's everywhere. if you live in new york city it might be gray because that's the most common color if you look around. idk
A conflict between a character and himself or herself
carbon and nitrogen because it is used as a source of nutrients for all matter