Final Answer:
The number that is a factor of 21 among the given options is C. 7.(Option C)
Step-by-step explanation:
To determine whether a number is a factor of 21, we need to check if it divides 21 without leaving a remainder. In this case, 7 is a factor of 21 because 21 รท 7 equals 3 with no remainder. Therefore, option C, 7, is the correct answer.
Factors are numbers that divide another number exactly. In the case of 21, its factors include 1, 3, 7, and 21. Factors are crucial in understanding the divisibility and relationships between numbers in mathematics. In this scenario, recognizing that 7 is a factor of 21 involves applying the fundamental concept of factors and divisibility.
Understanding factors is fundamental in various mathematical operations, including simplifying fractions, finding common denominators, and solving equations. In this context, recognizing the factor 7 provides a basis for further mathematical analysis and problem-solving.(Option C)