The correct answer is option 'D', which is spiral gearing. When two non-intersecting and non-coplanar shafts are connected by gears, the arrangement is known as spiral gearing. Let's explain this answer in detail.

**Explanation:**

**Shaft Arrangement:**
When we talk about shafts, we are referring to a mechanical component that is used to transmit torque and rotational motion. In some mechanical systems, it is necessary to connect two shafts together to transfer power or motion between them.

**Gearing:**
Gearing is a method of transmitting motion and power between two shafts by means of interlocking toothed wheels, known as gears. Gears can be used to increase or decrease the speed or torque of the driven shaft relative to the driving shaft.

**Types of Gearing:**
There are several types of gearing arrangements, including spur gearing, helical gearing, bevel gearing, and spiral gearing. Each type has its own advantages and is suitable for different applications.

- **Spur Gearing:** Spur gears are the most common type of gears and have teeth that are straight and parallel to the axis of the gear. They are simple and efficient but can produce noise and vibration due to the sudden engagement of teeth.

- **Helical Gearing:** Helical gears have teeth that are helically shaped, which allows for smoother engagement and quieter operation compared to spur gears. They can transmit higher loads and speeds, making them suitable for high-performance applications.

- **Bevel Gearing:** Bevel gears are used to transmit motion between intersecting shafts. Their teeth are cut on a conical surface, allowing for the transfer of motion at an angle. Bevel gears can transmit motion between shafts that are at any angle other than 90 degrees.

- **Spiral Gearing:** Spiral gears are a type of helical gears with teeth that are curved in a spiral shape. This design helps to reduce noise, vibration, and axial thrust, making them suitable for high-speed and high-load applications. Spiral gears provide smooth and continuous motion transfer between non-intersecting and non-coplanar shafts.

**Conclusion:**
When two non-intersecting and non-coplanar shafts are connected by gears, the arrangement is known as spiral gearing. Spiral gears provide efficient motion transfer with reduced noise and vibration, making them suitable for various applications in mechanical systems.