Concept:Computer viruses are malicious programs that spread through the exchange of infected files or data, not through physical typing actions.
Explanation:Viruses cannot move on their own; they attach to files or programs that are transferred between computers.
Downloading files from the internet can bring infected software or data into the system.
E-mail attachments often contain executables or macros that can carry viruses.
Pen drives (USB storage devices) can transfer infected files from one computer to another.
Typing on a keyboard simply sends key signals to the computer and does not transfer any external file or executable code.
Therefore, typing cannot introduce a virus into the computer system.
Answer:D. typing of keyboard