Areferendum is an election
a in which citizens can propose their own legislation.
b for judicial offices.
c for choosing party nominees for state offices.
d whereby voters are given the chance to approve or disapprove some legislative act or constitutional amendment.
e to determine whether to remove an elected official from office before the end of their term.

D) whereby voters are given the chance to approve or disapprove some legislative act or constitutional amendment.

Explanation:

A Referendum asks citizens their opinion on a specific issue, and they usually are given two options to vote, a "yes" or a "no" most of the time. For example, three years ago the United Kingdom held a referendum on whether it should leave or remain in the European union. The leave option won, and this started a complicated process known as "Brexit".

Referendums are a form of direct democracy and were common in ancient Athens. Nowadays, a country in which they are prevalent is Switzerland, where several referendums are held each year, on a wide array of issues, from land policy, tax reform or immigration.

the secretary of state, appointed by the president with the advice and consent of the senate, is the president's chief foreign affairs adviser. the secretary carries out the president's foreign policies through the state department and the foreign service of the united states.