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: A snowball is used to defend oneself against an alert .

SOLUTION: A chain is used to store oneself against an attack .

PROBLEM: When showering it is a good idea to wash beyond your ears .

SOLUTION: When showering it is a good idea to cross behind your ears .

PROBLEM: An Nuclear fireball creates a large explosion .

SOLUTION:
An ordinary bolt creates a large explosion .