Introduction:
A rigid flanged coupling is used to connect two shafts that are transmitting power. The coupling consists of two flanges that are bolted together. The bolts in the coupling play a critical role in transmitting the power between the shafts and ensuring the stability of the coupling.

Explanation:
The correct answer is option A, which means that the bolts in a rigid flanged coupling are subjected to shear force and bending moment. Let's understand why this is the case.

Shear force:
When power is transmitted through the shafts, it creates a torque. This torque is resisted by the bolts in the flanged coupling. The torque causes a shear force to act on the bolts, trying to shear them apart. The bolts need to be strong enough to withstand this shear force and prevent the coupling from failing.

Bending moment:
In addition to the shear force, the bolts in the flanged coupling also experience a bending moment. This bending moment occurs when the torque applied to the shafts causes a bending action on the bolts. The bending moment is higher at the flange where the torque is applied and decreases towards the other end of the bolt. The bolts must be able to withstand this bending moment without breaking.

Importance of the bolts:
The bolts in the flanged coupling are crucial for maintaining the integrity and stability of the coupling. They need to be properly tightened to ensure that they can resist the shear force and bending moment. If the bolts are not tightened enough, they may loosen over time and lead to failure of the coupling. On the other hand, if the bolts are tightened too much, they may exceed their elastic limit and fail under the applied load.

Conclusion:
In conclusion, the bolts in a rigid flanged coupling connecting two shafts transmitting power are subjected to shear force and bending moment. These forces need to be carefully considered and the bolts need to be properly designed and tightened to ensure the stability and integrity of the coupling.