Police Must Obtain a Court Order Before Installing a "Pen

Police must obtain a court order before installing a "pen register" because:

A) U.S.Supreme Court ruled that "pen registers" fall under the requirements of the Wiretap Act of 1968.
B) U.S.Supreme Court ruled that "pen registers" invade the reasonable expectation of privacy.
C) Congress passed laws requiring a court order be obtained before using a "pen register."
D) "pen registers" are illegal in the United States and can never be used by police.