The correct answer is answer B ("2, 1, 3, 5, 4").
In <u>sentence number 2</u>, the writer is introducing the main point she's trying to get across in the e-mail, which is that there's a specific problem with the rescheduling of an event.
<u>Sentence number 1</u> would know let us understand what exactly is causing this problem: the torrential rain left a disaster behind.
<u>Sentence number 3</u> follows up giving more details as to why this situation is a disaster and what the specific problem is: the ceremonial podium floated away.
In <u>sentence number 5</u>, we're being introduced to a new difficulty: a giant puddle.
Finally <u>sentence number 4</u> is developing on the previous one, adding that now there's a flock of ducks in that puddle and they won't let anyone near the place.
Hope this helps!