Answer:
A) online almanac
Explanation:
An online almanac is a publication that shows detailed information about particular events that happened in a given year. They are usually a publication with regards to weather, meteoreology, etc.
Therefore, the source that would provide the MOST detailed information concerning trends of floods and droughts during the early 1900's is an online almanac.
C, I think. A looks good, but B is missing a comma.
Option C: reverse word order
Thrilled - Very happy (Example: I was thrilled on my wedding day when I saw all of my family and friends.)
Congratulate - Say they are happy for her (Example: On my wedding day, my friends and family waited in line to congratulate us.)