C! To compare and contrast, you need two thing or more things to compare and contrast to!
In the excerpt, the word "pungent" refers to the pickles' aroma.
Pungent is a word to describe a very strong smell, very sharp and biting. So when Untermeyer used the word pungent to refer to the pickles, he was talking about their aroma, which is a fancy way to say smell.
He is called "Slam" because of his dunking ability
Both sentences A and B are capitalized correctly:
Only one solution is possible: We must cut our expenses.
Only one solution is possible: we must cut our expenses.
The first word of both sentences (only) must always be capitalized since it is placed at the beginning.
On the other hand, if the sentence following the colon is dependent (it is incomplete), its first word should not be capitalized. For example:
"I have to buy three things: apples, oranges and bananas."
Regarding capitalization in independent clauses following a colon (such as the one given in the example), it is subject to the citation style the writer is following (APA, MLA, etc). While some styles recommend capitalization of the first word of the sentence, some others do not.