Which of the following statements correctly explains what it means for DNA replication to be bidirectional?
(a) The replication fork can open or close, depending on the conditions.
(b) The DNA replication machinery can move in either direction on the template strand.
(c) Replication-fork movement can switch directions when the fork converges on another replication fork.
(d) The replication forks formed at the origin move in opposite directions.
Answer: D