Which statement BEST explains Lamarck's theory of acquired characteristics as it relates to the neck length of giraffes?
A) The DNA of the giraffe coded for longer necks in some individuals.
B) The variation in giraffe neck sizes led to some being more fit and able to survive.
C) Giraffes have always had long necks and this is not a characteristic that has ever changed.
D) Giraffes slowly stretched their necks to reach leaves higher in the tree and over time their necks got longer.