[单选题]
3. Which of the following are regarded a:/ccawb 3e 1qas possible causes of mutations in DNm,0(*l opewa mA?
I. Errors in DNA replication.
II. Mutagenic chemicals.
III. Advantageous traits in a parent.
IV. Some forms of radiation.
A. I and II only
B. II and IV only
C. I and III only
D. I, II and IV only