Final answer:
Duplications typically occur due to DNA replication errors when the DNA polymerase makes spontaneous errors that are not corrected, leading to sections of DNA being copied multiple times. The correct option is A.
Step-by-step explanation:
The most common way that duplications occur is through DNA replication errors. DNA replication is a complex process that is generally highly accurate, however, errors can still occur. An uncorrected mistake during DNA replication can lead to a duplication mutation, which is a type of mutation where a section of the DNA is copied one or more times.
These errors are often seen during the S phase in either meiosis or mitosis. Spontaneous errors by DNA polymerase during replication can cause these duplications without any external environmental influence.