Question

ugh!
sadly!
hurray!
finally, the delayed plane takes off, and the annoyed passengers cheer loudly.

Explanation:

The sentence describes annoyed passengers cheering loudly as their delayed plane finally takes off. "Hurray!" is an exclamation of joy and relief that matches this positive, relieved reaction. "Ugh!" expresses frustration, and "Sadly!" expresses sorrow, which do not fit the context of cheering passengers.

Answer:

Hurray!