Question

what is a line-item veto?
a power the president has to either veto or approve a bill only in its entirety
the power that the state supreme court has to declare certain parts of a law unconstitutional
a power that some state governors have to veto specific parts of a bill while passing the rest

Explanation:

A line-item veto allows an executive (like some state governors) to reject individual provisions ("line items") of a bill without vetoing the entire legislation. The U.S. President does not have this power (as per the Supreme Court's 1998 ruling), and judicial review of laws' constitutionality is separate from the line-item veto. Thus, the correct definition is the ability to veto specific parts while approving the rest.

Answer:

a power that some state governors have to veto specific parts of a bill while passing the rest