Their, since the sentence is refering to two people.
Answer:
The children <u>have found</u> the lost puppy
Explanation:
That's the correct sentence structure, if you use "is finding" or "have find" it just doesn't sound correct...
Answer:
this is a very long question
Based on my prior knowledge of the word I would say C (unoriginal) is a pretty safe choice.
use your imagination and you can copy a story from a movie you've watched and use that