Which of the Following Is Most Clearly an Explanation, Rather

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

A) Because there is a tornado watch in our county, we ought to go to our basement.
B) The virus was able to spread very rapidly because the residents of the town were not washing their hands frequently.
C) You shouldn't invest in that company because it has a track record of failure.
D) Contrary to popular belief, medieval people couldn't have believed that the Earth was flat, because they could see its round shadow on the moon during any lunar eclipse.
E) The snails in your box must be dead, because they have been in there for three days and you haven't given them any food.