In this task, you will be given a short story. One sentence from the story is chosen. Consider the events that happen before that sentence, or are likely to have happened before it. Does any of them directly cause it, or simply make it possible? You should write your answer in the form " A >causes/enables> B". Try to use phrases and sentences from the story to compose your answer when possible.

Let me give you an example: story: It was bedtime at our house. Two of the three kids hit the pillow and fall asleep. The third is a trouble maker. For two hours he continues to get out of bed and want to play. Finally he becomes tired and falls asleep.
 selected sentence: Finally he becomes tired and falls asleep.
The answer to this example can be: A kid wants to play before sleep >Causes/Enables> A kid eventually falls asleep
Here is why: The selected sentence is about a kid falling sleep, the answer correctly identifices an event causing the sentence to happen.

OK. solve this:
story: Sarah awoke one cold night to a strange noise coming from her window. She got out of bed to go see what it was. As she was walking to the window she saw a small shadow. She opened the curtain and was happily surprised. It was a tiny kitten scratching to get in from the cold.
 selected sentence: She opened the curtain and was happily surprised.
Answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Sarah hears a noise at her window >Causes/Enables> Sarah opens the curtains