To solve this question, the user needs to understand the concept of variable assignment and increment operators.

In the given code, we first declare an integer variable named "length" and assign it a value of 4. Then we use the increment operator "++" to increase the value of "length" by 1.

Now, let's go through each option and explain why it is right or wrong:

A. 4: This option is incorrect because the value of "length" is changed by using the increment operator. Therefore, the final value of "length" is not the same as its initial value of 4.

B. 5: This option is correct. The initial value of "length" is 4, and then we increment it by 1 using the "++" operator. Therefore, the final value of "length" is 5.

C. 6: This option is incorrect because if we use two increment operators in succession, then the value of "length" would be 6. However, in this code, there is only one increment operator, so the final value of "length" is 5.

D. 8: This option is incorrect because there is no operation in the given code that would result in the value of "length" being 8. The initial value of "length" is 4, and then we increment it by 1, resulting in a final value of 5.

Therefore, the correct answer is:

The Answer is: B. 5