Read this paragraph:

Backpacks are affecting children’s posture, says an article in Children’s Health Today.
Pediatricians treating back problems have noticed an increase in office visits from middle school- to high school-age children in certain communities. They attribute most of the visits to stress on the vertebra caused by textbooks students carry in their backpacks. They note fewer such visits in communities where online textbooks have become the norm.

If a reader wants to check the original source of information used in the paragraph, which words should the writer most likely hyperlink?
A. children’s health today
B. online textbooks
C. stress on the vertebra
D. note fewer such visits