Which if the following statements about the role of ddNTPs in Sanger sequencing is true.

A. Because they are missing both hydroxyl groups, once they are incorporated into the growing DNA strand they stop the polymerization reaction.
B. Because they contain a fluorescent group, once they are incorporated into the growing DNA strand they stop the polymerization reaction.
C. They do not stop the polymerization reaction, but incorporate fluorescence all along the newly synthesized DNA strand.
D. Because they are missing a phosphate group, once they are incorporated into the growing DNA strand they stop the polymerization reaction.