Answer:
c. a group of compromised computers connected to a network that attacks other networks
Step-by-step explanation:
Botnets refer to a group of computers controlled from a single source in which software programs are run. Botnets can be used for several purposes, such as scientific (SETI), or computing corporate purposes; on the other hand, botnets are also used for illegal purposes, for instance hacker run malicious programs in order to attack other networks.