This does not affect the argument. The author argues that not using calculators increases the likeliness of students remembering the principles—the argument isn’t about whether they understand them.

This does not affect the argument. The fact that slide rules were used several decades ago to learn math does not tell us about the advantages or disadvantages of using calculators when learning mathematical principles.

This strengthens the argument by supporting the author’s assumption that students’ ability to remember mathematical principles is a higher priority than an easier learning process.

This weakens the argument. It attacks the author’s assumption that there is value in the laborious process of applying mathematical principles (i.e., by increasing students’ retention of the material). Instead, it says easily-acquired habits are more valuable.

This does not affect the argument. The author’s argument is not about teachers’ enthusiasm, but about the reasonableness of restricting calculator use. We are looking for an answer choice that strengthens the idea that restricting calculator use is reasonable.