Ultra Violet rays or UV's cause the skin to burn in the sun.
True, children do go through many changes.
Answer:
I think The answer is sponge.
Explanation:
Condoms are also known as "barrier" methods of birth control; they physically block or otherwise prevent sperm from entering the uterus and reaching the egg for fertilization. The diaphragm, cervical cap, and sponge are used along with spermicide (a chemical substance that destroys sperm) to prevent pregnancy.
Likely the chronological age, mainly because it would explain the differences in puberty stages between the two boys, which is an example of physical maturation.
