Read the "one day's twilight line map". The map shows a complete morning line or dusk line. At this time, the earth's revolution speed is relatively fast. Answer the following questions. Sub-question 1: How long is the day of A land located on the morning line? Sub-question 2: How many hours is the day length of B when B is located on the faint line? Question 3: Which of the following options is correct if the sun is located at A, B, or somewhere between them? Question 4: Which of the following options is correct when the sun is directly above B?