For which compounds is the empirical formula the same as the molecular formula?

I.     Methane

II.     Ethene

III.     Ethanol

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B

One respondent commented that the question is unfair if candidates are not given the formula of the molecules. The examiners expect knowledge of simple molecules such as those in this question.