The correct answer is A: Successive approximation. Successive approximation is a type of analog-to-digital conversion (ADC). In successive approximation ADCs, the converter compares the input voltage to a series of reference voltages, successively refining the digital output until it matches the input. Successive approximation ADCs work by starting with the most significant bit (MSB) and working down. They compare the input to a reference, set the bit if the input is larger, then move to the next bit. This process continues until all bits are determined. Successive approximation ADCs provide a good balance of speed and accuracy and are commonly used in medium-speed applications. They're faster than integrating ADCs but slower than flash ADCs.