A study of native born residents in Newland found that two-thirds of the children developed considerable levels of nearsightedness after starting school, while their illiterate parents and grandparents, who had no opportunity for formal schooling, showed no signs of this disability. If the above statements are true, which of the following conclusions is most strongly supported by them?

• Only people who have the opportunity for formal ...........schooling develop nearsightedness.
• The nearsightedness in the children is caused by the ...........visual stress required by reading and other class work.
• Both A and B
• None