In Order to Obtain a Warrant Authorizing the Use of a "Pen

In order to obtain a warrant authorizing the use of a "pen register," the police must certify that:

A) information likely to be obtained is relevant in an ongoing criminal investigation.
B) if they use ordinary investigative techniques they will not be able to discover information needed in the investigation.
C) the phone line the device will be attached to belongs to an international crime ring.
D) All of these are necessary to obtain an authorization for a "pen register."