A. is higher for alkenes than it is for alkanes
B. is higher for alkynes than it is for alkenes
C. increases as the number of carbon atoms in the chain increases.
D. decreases as the number of carbon atoms in the chain increases.
Probably d is the answer that the author of the problem is looking for but it isn't always that one because branched chains don't always follow this rule. For example, look up the boiling point of n-pentane and all of its isomers.
C. increases as the number of carbon atoms in the chain increases.
