After a long flight we sure love to get a good sleep . But it 's afternoon in Beijing and we need to adjust to the local time . We took a quick nap and woke up in the early evening in time to take a stroll around the neighborhood . Our hostel is nearby the old drum tower which is located near a busy street .

Based on the preceding passage, choose your answer for question Why does a long flight require the speaker to then have to adjust to the local time ?
Options: I. None of the above choices .. II. Because they were the one flying the plane and therefore could not sleep. III. Because the flight was too noisy to sleep on and they are exhausted. IV. Once you 've entered a new region , your body must acclimate to the time difference.
The answer is:
IV.