A dip meter supplies the radio frequency energy which enables you to check:

The core of a dip meter is a variable-frequency radio frequency (RF) oscillator. By radiating this RF energy into a nearby unpowered circuit, the dip meter allows you to sweep across a range of frequencies until you find the exact point where the circuit absorbs the maximum energy. This point of maximum energy absorption is visually indicated by a dip on the instrument's meter and indicates the resonant frequency of the circuit under test. You then simply read that resonant frequency directly off the instrument's calibrated dial. A dip meter is not designed to measure impedance mismatch (which requires an SWR bridge) or to calibrate a wavemeter, making the other options incorrect.