Sequential circuits are a type of digital circuit that have memory elements, which allow them to store information and use it to determine the output. These circuits have flip-flops or latches that can hold a state or value. The output of a sequential circuit is influenced not only by the present input values but also by the past output values.

Past Output Values:
The output of a sequential circuit is dependent on the past output values because the current output is influenced by the previous state of the circuit. The output at any given time is determined by the combination of the current inputs and the previous output values. This is because the circuit retains its state and uses this information to calculate the next output.

Intermediate Values:
Sequential circuits also rely on intermediate values to calculate the output. These intermediate values are the internal states or values within the circuit that are not directly observable but are crucial for the operation of the circuit. The intermediate values are the result of the combinational logic within the circuit, which processes the input and the current state to produce the next state.

Both Past Output and Present Input:
The correct answer is option 'C' because sequential circuits consider both the past output values and the present input values to determine the output. The current input values provide the information necessary to calculate the next state, while the past output values maintain the circuit's memory and affect the current output.

Sequential circuits are commonly used in applications where memory is required, such as in counters, shift registers, and memory units. By considering both the past output values and present input values, these circuits can perform complex operations and store information, making them essential in digital systems.