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 of the problems we had with this year's Christmas party, we will need to start preparing for next year's much earlier.
B) Since the dodo was a bird, it probably tasted a lot like chicken.
C) The Sun will rise in the east tomorrow, since the Earth is spinning eastward.
D) We ought to vacation in Aruba next year, because the tickets are cheap.
E) The right to free speech must be limited, since we would otherwise have to permit slander and incitement of riots.