Hello Xingyu,
Thank you for your question.
I guess you refer to the questions with the blank text boxes to write the answer (Part 3 - questions 6 and 9).
The questions are graded automatically, meaning that once you submit the attempt, you will immediately get approximate grade feedback that includes these two answers in your performance.
For question 6, where you are expected to list differences for IPv4 and IPv6, try to be precise. What do you see in one case and what in the other?
Earlier today, we added additional information to question 9, which will help you solve it.
Kind regards,
Dubravka