Step 1: Understanding the principle.
The principle clearly states that an accident which is physically unavoidable, even after taking reasonable care, serves as a valid defence under the law of torts.
Step 2: Analyzing the facts.
In the given situation, the road was muddy due to heavy rain, and a biker suddenly crossed in front of the bus. The bus driver applied brakes immediately to avoid hitting the biker. Despite driving at a moderate speed and exercising due care, the bus skidded, leading to a collision with another bus.
Step 3: Application of legal concept.
The accident occurred despite the drivers’ best efforts and without negligence. Such an event, which could not have been avoided even with reasonable caution, qualifies as an inevitable accident under tort law.
Step 4: Elimination of incorrect options.
(A) Self defence: This applies when force is used to protect oneself, which is not relevant here.
(C) Act of God: This involves natural forces without human intervention; here, human actions were involved.
(D) Necessity: This defence applies when harm is caused to prevent a greater harm, which is not the case here.
Step 5: Conclusion.
Since the accident was unavoidable despite reasonable care and caution, the correct derivation is inevitable accident.