A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a computer virus, a metaphor derived from biological viruses
D, an acrostic is a "a poem, word puzzle, or other composition in which certain letters in each line form a word or words."
In this exercise, we have to use computer knowledge to define mainframe, so it is an integrated computer platform capable of processing large volumes.
<h3>What is a Mainframe Computer?</h3>
Mainframe is an integrated computer platform capable of processing large volumes of information in short periods of time. Currently, these platforms offer services to thousands of users through numerous terminals – directly connected or networked – using modern and flexible software.
See more about mainframe at brainly.com/question/5563113
Since there is no D, your closest answer is C.
The answer is not a, because you can make the sign by putting c in-between parenthesis (c). (Works usually on Google).
The answer is not + either, as it is located on the keyboard.
Hope this helps