The correct answer is: D. None of the above
The word “until” is used to indicate a point in time at which something will happen or end. For example, “I will stay here until you come back.” The word “over” is used to indicate that something has been completed or finished. For example, “The game is over.” The word “between” is used to indicate the space or time that separates two things. For example, “The meeting is between 10am and 12pm.”
In the question “How long is it . . . . . . . . summer vacation?”, the word “until”, “over”, and “between” do not make sense. This is because the question is asking about the length of summer vacation, not the time at which it will end, whether it is finished, or the space or time that separates it from something else.
Therefore, the correct answer is “None of the above”.