When Predictions Are Made from the Genome of a Species

When predictions are made from the genome of a species alone, they may prove to be wrong for several reasons. What is one of those reasons?

A) The function predicted by extrapolation from already known genes always matches the current function.
B) Even if the function is known, the expression pattern may differ.
C) The function predicted by extrapolation may vary extensively within individuals of the species.
D) Often, the introns within species vary too much between individuals.