The least prime number is

### Concept & Logic The core concept is the fundamental definition of a prime number. A prime number is defined as a natural number greater than $1$ that has exactly two distinct positive divisors: $1$ and the number itself. ### Step-by-Step Solution Let's evaluate the given options based on the definition of prime numbers: * **Option (a) 0:** $0$ is not a natural number (in most standard definitions used in these exams) and it is divisible by every number, so it is not prime. * **Option (b) 1:** $1$ has only one positive divisor (itself). Since it does not have exactly two distinct divisors, it is strictly classified as neither prime nor composite. * **Option (c) 2:** $2$ is a natural number greater than $1$. Its only divisors are $1$ and $2$. Thus, it is a prime number. * **Option (d) 3:** $3$ is also a prime number, but it is larger than $2$. Therefore, the smallest (least) prime number is $2$. ### Exam Strategy & Shortcut This is a pure knowledge-based question that should take less than two seconds. Memorize the basic classification of numbers: $2$ is the first prime number and the *only* even prime number. ### Common Pitfall The most common mistake is selecting $1$ because it is the first positive integer or the smallest odd number. Remember that $1$ is a special case in number theory and is excluded from being prime to maintain the uniqueness of prime factorization. ### Final Answer Therefore, the correct answer is 2.