Explanation:

To find the perfect square number between 30 and 40, we need to consider each number in that range and check if it is a perfect square.

Definition of a Perfect Square:
A perfect square is a number that can be expressed as the product of an integer multiplied by itself. For example, 4, 9, and 16 are perfect squares because they can be expressed as 2x2, 3x3, and 4x4 respectively.

Method:
We can start by checking each number between 30 and 40 and determine if it is a perfect square.

Checking for Perfect Squares:
- Start with the number 31: 31 is not a perfect square because there is no integer whose square is equal to 31.
- Next, check the number 32: 32 is not a perfect square because the square root of 32 is a decimal value, approximately 5.6568.
- Move on to the number 33: Similar to 31 and 32, 33 is also not a perfect square.
- Continuing this process, we reach the number 34, which is also not a perfect square.
- The number 35 is the next in line. Let's check if it is a perfect square.

Checking if 35 is a Perfect Square:
- The square root of 35 is approximately 5.9161, which is a decimal value.
- Therefore, 35 is not a perfect square.

Checking the Remaining Numbers:
- We proceed to check the numbers 36, 37, 38, and 39.
- When we reach the number 36, we find that it is a perfect square because it can be expressed as 6x6, where 6 is an integer.
- However, we continue checking the remaining numbers to ensure that 36 is the only perfect square in the given range.

Final Answer:
Among the numbers 30 to 40, the only perfect square is 36. Therefore, the correct answer is option 'C'.