Which verb form is used to indicate the perfect tense? a. verb + -ed b. be + verb + -ing c. have + been + verb + -ing d. have + verb + -ed

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 theoretical breakthrough would be a fundamentally new way of finding alice's private key mathematicians have been studying factoring for centuries, and modern factoring techniques are not significantly better than ancient techniques a more recent development is the so-called tempest attack, which aims to detect the electromagnetic signals emitted in a computer's display unit if scientists could build a quantum computer, it would be able to perform calculations with enormous speed mark this and return save and exit next submit