Answer:
B. making sure federal agencies do their jobs.
Step-by-step explanation:
Gerrymandering is redrawing the electoral boundaries of a certain area to benefit one political party. This is not fair and is therefore not a responsibility.
The branch that has to do with deciding if something is unconstitutional or not is the judicial branch. The Supreme Court, for example, would interpret the Constitution to see if something is constitutional.
The President is the one that vetoes laws from Congress, not the other way around.
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