Which effect of technology is shown in the comparison of telebook and printed book?

Correct answer: The medium of study changed

The governing concept is the effect of technology on the medium of education and reading. In the story, Margie and Tommy are accustomed to telebooks, which appear on a screen and can be read electronically, whereas the old book found by Tommy consists of printed words on paper. This contrast shows that technology has changed the physical form through which children receive information. It does not suggest that children stopped reading, that geography disappeared, or that the number of human teachers increased. Therefore, option A is the most precise answer because it identifies a change in the medium of study without making an exaggerated claim about learning itself.