TASK DEFINITION: Given a sentence, generate a new sentence by performing small changes on the sentence. Here, make sure that the changes are semantically related and syntactically similar to the input. And the generated sentence should have high commonsense plausibility, that is to have reasonable probability of it being true.
PROBLEM: To open a locked door you usually need to have a buddy .

SOLUTION: To open a locked door you usually need to have a key.

PROBLEM: When everyone in the world is slaughtered , it 's a world war .

SOLUTION: When everyone in the world is fighting, it's a world war.

PROBLEM: You would erase a language because you see to speak with the neighbors .

SOLUTION:
You would exchange a language because you want to hide with the neighbors .