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: An x is used for communicating through the postal system .

SOLUTION: An envelope is used for reading through the postal system .

PROBLEM: You can use steel to build a bridge.

SOLUTION: You can use inheritance to identify a transition .

PROBLEM: The effect of fighting the enemy is someone does .

SOLUTION:
The effect of fighting the enemy is someone becomes .