Answer:
a. Our, It's
Explanation:
The first letter of a sentence must always be capitalized. In this case, we have two sentences, since one is between quotation marks. Even though it is not the first letter before a period, it still is the first letter of a sentence and it does follow the rules for capitalization. Also, it should be It's instead of its.
So, it should be:
Our travel agent said, "It's one of the most exciting places in the world."