Answer:
A. Increasing textbook prices led a significant number of students to opt for used books or rely on library reserves instead of purchasing new textbooks.
C. The enhancements in calculator quality and design from 2017 to 2019 were substantial. For instance, 2019 calculators now accommodate memory cards, which older versions do not, though measuring this quality shift can be challenging.
D. A novel, secure method for enhancing memory was launched for sale.
Rationale:
Option A is valid since rising textbook costs imply heightened inflation, resulting in increased college expenses. Consequently, students may prefer used texts or forego purchases altogether.
In Option C, while it's stated that calculator quality improved in 2019, this might also contribute to higher pricing, which is typically emphasized in surveys.
Option D suggests the introduction of improved memory enhancement techniques.