Answer:
A. What are you talking about, Marcus? Asked Shelby.
Explanation:
The correct way of writing the above sentence will be
"What are you talking about, Marcus?" asked Shelby.
As the sentence is based on a conversation, inverted commas should be used to open the sentence as well as close it. The rest of the options are indirect speeches while the first option is a direct speech. Thus, the punctuation.
Answer:
To experience nature at its fullest requires mental effort.
Treaty of Versailles is the correct capitalization for this subject.
Generally the word treaty is lowercase, but in this instance the complete title is Treaty of Versailles, so you would capitalize it.