Explanation:

The state amplifier has no input is referred to as the "Empty-signal condition". Let's understand why this is the correct option.

Zero signal condition:
- The "Zero signal condition" refers to the situation where the input signal to the amplifier is reduced to zero or negligible levels.
- In this condition, the input signal is practically non-existent, but the amplifier still operates and produces an output signal.
- This condition is commonly encountered when the input source is disconnected or when the input signal is attenuated significantly.

Non-signal condition:
- The "Non-signal condition" can be considered as a general term that encompasses any situation where there is no input signal present.
- It can include scenarios where the input signal is zero or negligible, as well as situations where the input source is completely disconnected.

Quiescent condition:
- The "Quiescent condition" refers to the steady-state operating point of an amplifier when no input signal is applied.
- In this condition, the amplifier operates in a stable and bias-corrected state, ready to amplify any input signal that is provided.
- The quiescent condition is essential for establishing the proper biasing levels and ensuring the amplifier operates within its specified parameters.

Empty-signal condition:
- The "Empty-signal condition" is the correct term to describe the state amplifier with no input signal.
- This condition specifically indicates that there is no input signal present, which means there is no signal to be amplified or processed by the amplifier.
- The amplifier may still be powered on and operational, but it is not receiving any input signal to amplify.

In summary, while options a) Zero signal condition, b) Non-signal condition, and c) Quiescent condition may all describe situations where there is no input signal, the term "Empty-signal condition" specifically refers to the state amplifier with no input signal present. Therefore, option d) is the correct answer.