The voltage drop at brush-commutator contact is variable (1-2V) and independent of armature current.

**Explanation:**

The statement is false. The voltage drop at the brush-commutator contact is not variable and not dependent on the armature current. Let's discuss why.

**1. Brush-Commutator Contact:**
The brush-commutator contact is an essential part of a DC motor or generator. It is responsible for transferring current between the stationary brushes and the rotating commutator segments. The contact between the brushes and commutator must be reliable to ensure efficient power transfer.

**2. Voltage Drop at Brush-Commutator Contact:**
When current flows through the brush-commutator contact, there is a voltage drop due to the resistance and impedance of the contact. This voltage drop is typically referred to as the "brush drop" or "commutation voltage drop."

**3. Factors Affecting Brush Drop:**
The voltage drop at the brush-commutator contact is influenced by several factors, such as:

- Brush Material: Different brush materials have different electrical resistivities, which can affect the brush drop.
- Brush Pressure: The pressure applied by the brushes on the commutator affects the contact resistance and, consequently, the brush drop.
- Brush Size and Shape: The size and shape of the brushes also play a role in determining the brush drop.
- Commutator Condition: The condition of the commutator surface, including its cleanliness and smoothness, affects the brush drop.

**4. Armature Current and Brush Drop:**
While the armature current is an important parameter in a DC machine, it does not directly determine the voltage drop at the brush-commutator contact. The armature current affects the overall voltage drop across the machine, including the armature resistance drop and other losses.

**Conclusion:**
In conclusion, the voltage drop at the brush-commutator contact is not variable and not dependent on the armature current. It is influenced by factors such as brush material, brush pressure, brush size and shape, and commutator condition. The armature current affects the overall voltage drop in the machine, but not specifically at the brush-commutator contact. Therefore, option 'B' is the correct answer.