Explain why it is important to know if a time is in the a. m or in the p. m when figuring out how much time elapsed

Are there any answers like A. B. C. D.

Times in the a. m. and p. m. are separated by 12 hours. 6:00a. m. is 12 hours before or after 6:00p. m. So, if you use them incorrectly, your answer will be off by 12 whole hours! Let's say you want to know how much time there is between 3:00a. m. and 5:00a. m. That would be 2 hours. But if it's 5:00p. m., then the time elapsed would be 14 hours! See the major difference?