Consider the Compounds Named Below

Consider the compounds named below. Use the letter of the substance to answer the following questions. Some letters may be used more than once. Some questions may have more than one correct answer. In the latter case, only one letter need be given.
-The compound with the lowest boiling point is represented by the letter ______.

A) propene
B) 1-butene
C) 2-butene
D) 1-pentene
E) 2-pentene