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: The effect of helping someone is improving a situation.

SOLUTION: The habit of helping someone is improving a situation .

PROBLEM: If you want to play cards then you should find a willing opponent.

SOLUTION: If you want to play cards then you should find a playable opponent .

PROBLEM: A teacher can mark a fact .

SOLUTION:
A teacher can explain a fact.