[单选题]
2. Which of the folldt p-cpu9e(-v (vawbmn; q lme3v p1.8owing can be used to classify organisms into clades?
I. Common ancestry.
II. Shared morphological characteristics.
III. DNA base sequences.
IV. Chromosome number.
A. All of the above
B. IV only
C. I, II and III only
D. I, III and IV only