**Answer:**

The correct answer is option **B) saturation**.

When an n-transistor conducts and has a large voltage between the source and drain, it is in the saturation region. The saturation region is one of the three operating regions of a field-effect transistor (FET), the other two being the cut-off region and the linear (or triode) region.

In the saturation region, the n-transistor is fully turned on and is conducting a large amount of current between the source and drain terminals. The voltage between the source and drain (known as drain-source voltage or Vds) is typically high in this region.

To understand why the saturation region is the correct answer, let's briefly discuss the other regions of operation for an n-transistor:

1. **Cut-off region:** In the cut-off region, the n-transistor is turned off and there is no current flowing between the source and drain. The drain-source voltage is typically zero or very low.

2. **Linear (or triode) region:** In the linear region, the n-transistor is partially turned on and conducts a moderate amount of current between the source and drain. The drain-source voltage is typically moderate in this region.

Now, let's discuss why the saturation region is the appropriate answer:

**1. Large Voltage between Source and Drain:**

In the question, it is mentioned that the n-transistor has a large voltage between the source and drain. This implies that the drain-source voltage (Vds) is high. In the saturation region, the drain-source voltage is indeed high, which aligns with the given information.

**2. Conducting Transistor:**

The question also states that the n-transistor is conducting. In the saturation region, the transistor is fully turned on and allows a large amount of current to flow between the source and drain. Therefore, the transistor is conducting as mentioned in the question.

**Conclusion:**

Based on the given information, when an n-transistor conducts and has a large voltage between the source and drain, it is in the saturation region. In this region, the transistor is fully turned on and allows a large amount of current to flow between the source and drain terminals.