Sexual Response Can Be Seen at the Earliest

Sexual response can be seen at the earliest

A) between ages 5 and 6 years, when children begin to masturbate.
B) around age 12 months, when boys begin to have erections.
C) shortly before puberty, when boys begin to have erections and girls show vaginal lubrication.
D) during infancy, when boys experience erections and girls experience clitoral erections.