The correct answer is D. principle.
A principle is a fundamental truth or proposition that serves as the foundation of a system of belief or behavior. In the context of religion, a principle is a belief that is considered to be essential to the religion. For example, one of the principles of Christianity is the belief in God.
The other options are incorrect. A principal is a person who is in charge of a school or other organization. A prinsipal is not a word in the English language. A prinsiple is a misspelling of the word “principle.”
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