One of the author’s purposes in The Code Book is to explain different types of codebreaking to his readers. Which line best demonstrates this purpose?
A
a theoretical breakthrough would be a fundamentally new way of finding Alice's private keyB
mathematicians have been studying factoring for centuries, and modern factoring techniques are not significantly better than ancient techniquesC
a more recent development is the so-called tempest attack, which aims to detect the electromagnetic signals emitted . . . in a computer's display unitD
if scientists could build a quantum computer, it would be able to perform calculations with . . . enormous speed