(4)) Which is a composite number? \( \begin{array}{llll}\text { (4)) } 21 & \text { (4)) } 29 & \text { (f) } 23 & 43\end{array} \)

To determine which of the given numbers is a composite number, we first need to understand the definitions: - A **composite number** is a positive integer that has at least one positive divisor other than one or itself. In other words, it can be divided evenly by numbers other than 1 and itself. - A **prime number** is a positive integer greater than 1 that has no positive divisors other than 1 and itself. Now, let's analyze each of the given numbers: 1. **21**: - Divisors: 1, 3, 7, 21 - Since it has divisors other than 1 and itself, 21 is a composite number. 2. **29**: - Divisors: 1, 29 - Since it has no divisors other than 1 and itself, 29 is a prime number. 3. **23**: - Divisors: 1, 23 - Since it has no divisors other than 1 and itself, 23 is a prime number. 4. **43**: - Divisors: 1, 43 - Since it has no divisors other than 1 and itself, 43 is a prime number. From this analysis, the only composite number among the options is **21**.