Step 1: Understanding Article 14
Article 14 of the Indian Constitution states, "The State shall not deny to any person equality before the law or the equal protection of the laws within the territory of India." This article contains two concepts:
\begin{enumerate}
Equality Before Law: This is a negative concept, implying the absence of any special privileges in favour of any individual. It means that everyone is subject to the ordinary law of the land, and no person is above the law.
Equal Protection of the Laws: This is a positive concept, implying that the law should be applied equally and without discrimination to all persons who are similarly situated.
\end{enumerate}
The question specifically asks about the source of "equality before law".
Step 2: Identifying the Source
The concept of "Equality Before Law" is of British origin. It is a key element of the concept of 'Rule of Law', as propounded by the British jurist A.V. Dicey.
The concept of "Equal Protection of the Laws" has been taken from the American Constitution (specifically the 14th Amendment).
Step 3: Evaluating the Options
Since the question asks for the source of "equality before law", the correct answer is the British Constitution.
Step 4: Final Answer
The concept of equality before law is adapted from the British Constitution. Therefore, option (D) is the correct answer.