The graph shows the incidence of trisomy resulting from non-disjunction in pregnancies at different maternal ages.

[Source: Center for Disease Control]
What can be inferred from the graph?
A. The incidence of three copies of a chromosome increases directly in proportion with the age of the mother.
B. The incidence of three sets of chromosomes increases from age 20.
C. The incidence of three copies of a chromosome increases the most from age 35.
D. The incidence of three sets of chromosomes increases the most from age 30.