Madelyn allowed her sister's words to swirl around and swell up in her brain. She wanted to give an eloquent response, but she realized

words alone would not soothe her sister. They both were painfully aware that Madelyn's decision to study abroad for a year would be difficult; the

sisters had been inseparable since childhood. Thrilled by the opportunity for her sister, and yet saddened by the thought of physical distance,

Madelyn was resolved to express nothing but enthusiasm and support. Fluent in German, her sister often spoke of immersing herself in German

culture and exploring its picturesque countryside. As far as Madelyn was concerned, the decision was irrevocable; rather than argue against it, she

would help her sister prepare for the exciting adventure. After much discussion, the sisters pledged to write daily, to keep photography journals,

and to document their experiences online. They talked happily and contentedly late into the night, realizing that nothing could ever truly separate

them.

What is the meaning of irrevocable as it is used in the paragraph?

1. Inconvenient
   
2. Indefinite
   
3. unchangeable
   
4. unfortunate