Concept:The pattern "It is about time" needs a past-tense verb to show that an action is overdue.
Explanation:The expression "It is about time" refers to something that should already have happened or should happen now.
In English, this structure requires the simple past form of the verb.
The base verb in the sentence is "go".
Its simple past form is "went".
Hence, the correct sentence is: "It is about time you went to bed."
This means that you are late in sleeping and you should go to bed immediately.
"Go" and "have gone" do not follow the "about time" pattern.
"Should go" is sometimes possible in formal grammar, but "went" is the natural and expected answer in this context.
Answer:Option C. "went"