Prime Factors of 84:
To determine the prime factors of 84, we need to find the prime numbers that divide evenly into 84. A prime number is a number greater than 1 that is only divisible by 1 and itself.

Step 1: Prime factorization of 84:
To begin, we can start by dividing 84 by the smallest prime number, which is 2.

84 ÷ 2 = 42

Now, we have a new number, 42. We continue dividing by 2 until we can no longer divide evenly.

42 ÷ 2 = 21

Again, we have a new number, 21. We continue dividing by 2.

21 ÷ 2 = 10.5 (not divisible evenly)

2 is the only prime factor of 84 that we have found so far.

Step 2: Continue with the next prime number:
Since 2 is not a factor of 21, we move on to the next prime number, which is 3.

21 ÷ 3 = 7

Now, we have a new number, 7. We continue dividing by 3.

7 ÷ 3 = 2.33 (not divisible evenly)

3 is another prime factor of 84 that we have found.

Step 3: Final prime factor:
Since 3 is not a factor of 7, we move on to the next prime number, which is 5.

7 ÷ 5 = 1.4 (not divisible evenly)

5 is not a prime factor of 84.

Summary:
In conclusion, the prime factors of 84 are 2 and 3. Thus, the correct answer is option A, which is 2.