A device used to display one or more digital signals so that they can be compared to expected timing diagrams for the signals is a:

ANS:C - logic analyzer

A multimeter or a multitester, also known as a VOM (Volt-Ohm meter) , is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter would include basic features such as the ability to measure voltage, current, and resistance. Multimeters may use analog or digital circuits-analog multimeters (AMM) and digital multimeters (often abbreviated DMM or DVOM. ).

SPECTRUN ANALYSER:

A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals.

FREQUENCY COUNTER:

A frequency counter is an electronic instrument, or component of one, that is used for measuring frequency. Frequency is defined as the number of events of a particular sort occurring in a set period of time. Frequency counters usually measure the number of oscillations or pulses per second in a repetitive electronic signal. Such an instrument is sometimes referred to as a cymometer.