The device that generates the basic timing clock signal for the operation of the circuit using a crystal oscillator is an oscillator.

An oscillator is an electronic circuit that generates a periodic waveform on its output without any external input. It uses a feedback loop to continuously generate and sustain the oscillations. In the case of a crystal oscillator, it uses a quartz crystal as its resonant element.

Here is a detailed explanation of why the correct answer is option 'C', the oscillator:

1. Timing Unit: A timing unit is a component that measures and controls the timing of operations in a circuit or system. It is responsible for generating accurate and synchronized timing signals. While a timing unit may use an oscillator as a fundamental component, it is not the device that generates the basic timing clock signal itself.

2. Timing and Control Unit: A timing and control unit is a more comprehensive component that combines timing and control functions. It is typically used in complex systems to manage the timing of various operations and control the flow of data. While it may include an oscillator as a subcomponent, it is not the primary device responsible for generating the basic timing clock signal.

3. Oscillator: An oscillator is the device that generates the basic timing clock signal for the operation of the circuit. It is a self-contained circuit that produces a continuous waveform with a specific frequency and amplitude. In the context of crystal oscillators, a quartz crystal is used as the resonant element to provide high stability and accuracy in the generated waveform.

4. Clock Generator: A clock generator is a specific type of oscillator that is designed to generate clock signals. It may incorporate additional features such as frequency dividers, phase-locked loops, or programmable outputs. While a clock generator can be used to generate the basic timing clock signal, the more general term "oscillator" is preferred in this context.

In summary, the device that generates the basic timing clock signal for the operation of the circuit using a crystal oscillator is an oscillator. It is responsible for producing a continuous waveform with a specific frequency and amplitude, using a feedback loop and a quartz crystal as the resonant element.