Dual-slope ADC:
The dual-slope ADC is a type of analog-to-digital converter that works by integrating the input voltage over two different time periods. It is also known as the integrating or ramp type ADC. The first phase of the conversion involves integrating the input voltage for a fixed period of time, and then the second phase involves discharging a capacitor at a known rate. The time required to discharge the capacitor is proportional to the input voltage, and this time is measured to determine the digital representation of the analog input.

Counter-type ADC:
The counter-type ADC, also known as a counter-ramp ADC, is a type of analog-to-digital converter that uses a counter to convert the input voltage into a digital value. It works by applying the input voltage to a comparator, which compares it with a reference voltage. The counter starts counting when the input voltage is higher than the reference voltage and stops when they are equal. The count value is then converted into a digital representation of the analog input.

Tracking-type ADC:
The tracking-type ADC, also known as a sample and hold ADC, is a type of analog-to-digital converter that samples the input voltage periodically and holds it constant during the conversion process. It uses a sample and hold circuit to sample the input voltage and then converts it into a digital representation using a comparator and a successive approximation register.

Successive approximation ADC:
The successive approximation ADC is a type of analog-to-digital converter that uses a binary search algorithm to determine the digital representation of the analog input. It works by comparing the input voltage with the output of a digital-to-analog converter (DAC) and adjusting the DAC's output based on the result of the comparison. This process is repeated iteratively until the digital representation converges to the desired accuracy.

Continuous Conversion Type ADC:
The continuous conversion type ADC is a type of analog-to-digital converter that continuously samples and converts the input voltage into a digital representation without interruption. It operates by continuously comparing the input voltage with a reference voltage and updating the digital output accordingly. This type of ADC is commonly used in applications where a continuous stream of analog data needs to be converted into digital format in real-time.

Therefore, the correct answer is option 'D' - Successive approximation ADC.