Correct Way of Counting by 7:

To count by 7 correctly, we need to add 7 to the previous number each time. The correct sequence is as follows:

c) 7, 14, 21, 28

Explanation:

To understand why option 'C' is the correct way of counting by 7, let's analyze each option:

a) 28, 42, 14, 21

This sequence is not counting by 7. It starts with 28, then jumps to 42, which is an increment of 14. Then it goes back to 14, which is a decrement of 28. Finally, it jumps to 21, which is an increment of 7. Therefore, option 'a' does not follow the correct pattern of counting by 7.

b) 42, 28, 21, 14

Similar to option 'a', this sequence also does not follow the correct pattern of counting by 7. It starts with 42, then jumps to 28, which is a decrement of 14. Then it goes to 21, which is a decrement of 7. Finally, it jumps to 14, which is a decrement of 7. Therefore, option 'b' is not the correct way of counting by 7.

c) 7, 14, 21, 28

This sequence is the correct way of counting by 7. It starts with 7 and adds 7 to the previous number each time. So, when we add 7 to 7, we get 14. When we add 7 to 14, we get 21. And when we add 7 to 21, we get 28. Therefore, option 'c' is the correct way of counting by 7.

d) All of these

This option is incorrect because options 'a' and 'b' are not the correct ways of counting by 7. Only option 'c' follows the correct pattern. Therefore, the correct answer is option 'C'.

Summary:

To count by 7 correctly, we need to start with 7 and add 7 to the previous number each time. The correct sequence is 7, 14, 21, 28. Options 'a' and 'b' do not follow this pattern, so the correct answer is option 'C'.