Which of the Following Would Best Explain Why Most People

Multiple Choice

Which of the following would best explain why most people are sick more often as children than as adults in their 20s through 50s?

A) The immune system does not appear until the preteen years.
B) In children, the thymus is so active in fighting bacteria that it produces stronger symptoms of disease.
C) Because of their small size, children's bodies cannot contain as much lymphoid tissue as those of adults.
D) During childhood, we build up many varieties of memory lymphocytes, which provide immunity to more and more antigens during adulthood.