You cannot put any sort of endmark (period, question mark, or exclamation point) here because it is not a complete sentence. Complete sentences must have a subject and a predicate. You can tell there's not even a verb here, so this is just a fragment, and we would have to use a comma.
a. Very truly yours,
Answer:
I found one... "desert" it should be dessert two s's
Explanation:
Answer:
The valley of Ashes is a massive trash dump full of smoke and from Nick's description it is a horrible place where you would not want to be.
Explanation:
Answer:
b. looking at the window i saw rain started falling
