**Answer:**

To understand how the generated torque varies with the applied current in a universal motor, we need to consider the torque-speed characteristics of the motor.

**Torque-Speed Characteristics of a Universal Motor:**
- A universal motor is a type of electric motor that can operate on both AC and DC power sources.
- It is commonly used in applications where high torque and variable speed are required, such as power tools and vacuum cleaners.
- The torque-speed characteristics of a universal motor are non-linear and can be represented by a graph.

**Rated Supply Current and Rated Torque:**
- The rated supply current of 10A corresponds to the maximum current that can be safely drawn from the power source to operate the motor.
- The rated torque of 100 N-m corresponds to the maximum torque that the motor can produce when operated at the rated supply current.

**Relationship between Current and Torque:**
- In a universal motor, the torque produced is directly proportional to the current flowing through the motor windings.
- Therefore, if a current of 5A is applied, the generated torque will be half of the rated torque.

**Calculation:**
- Given that the rated supply current is 10A and the rated torque is 100 N-m.
- When a current of 5A is applied, the generated torque can be calculated using the formula:
Generated Torque = (Applied Current / Rated Current) * Rated Torque
= (5A / 10A) * 100 N-m
= 50 N-m
- Therefore, the generated torque when a current of 5A is applied is 50 N-m.

**Conclusion:**
- The generated torque will vary linearly with the applied current in a universal motor.
- In this case, when a current of 5A is applied, the generated torque will be 50 N-m, which is half of the rated torque of 100 N-m.
- Therefore, the correct answer is option 'B' - 400 N-m.