Answer:
B. The president vetoes a bill.
Explanation:
The system of check and balances is the system whereby all three branches of the government oversees, limit and check each other so no branch abuses from its powers. Through this principle, each branch can respond to the action of the other.
For example, under this system, the Legislative branch is responsible for proposing and passing bills, however, bills cannot become law until they are sent to the President (the head of the Executive branch) for signature. The President can impose a check on that Congress' power by vetoing the bill. If the President vetoes the bill, then it has to go back to Congress, which has the opportunity to override that veto with enough votes.
