Which of the following is a response a receiving controller may use when they locate a target?

When a receiving controller successfully locates a target, the appropriate response is to acknowledge it, which can be facilitated by using standard communication procedures. The phrase "Point Out Approved" is specifically used to indicate that the receiving controller has confirmed and is aware of the target's location and is preparing to manage its traffic accordingly.

This phrase is especially important when there's a transfer of communication about an aircraft from one controller to another. It signifies that the receiving controller has either visually acquired the target or has been alerted to its existence and is ready to take responsibility for providing instructions to the aircraft based on the information received.

Other responses such as "Radar Lost," "Clear for Descent," and "Altitude Unverified" serve different purposes in air traffic control communication. "Radar Lost" indicates a failure to track a target, which is a different scenario. "Clear for Descent" is an instruction to the pilot for altitude change, and "Altitude Unverified" suggests that the altitude information on the target has not been confirmed. None of these directly relate to the acknowledgment of successfully locating a target, which is why "Point Out Approved" is the most appropriate response in this context.