Which of the Following Is Most Clearly an Explanation Rather

Which of the following is most clearly an explanation rather than an argument?

A) The mail arrived late today because there was an automotive accident near the post office.
B) We will certainly have a manned mission to Mars within the next 30 years because we are devoting so much effort to preparing for it.
C) The next president will be tall since, historically, most presidents have been tall.
D) This bill should be enacted into law since it will help many people.
E) Since American students are falling behind in science and mathematics, American schools should approach these subjects differently.