To answer this question, you need to understand the common sources of viruses that can infect the hard disk of a computer. Let's go through each option to understand why it is correct or incorrect:
Option A) Incoming Email - This option is correct. Incoming emails can often contain attachments or links that may contain viruses. Clicking on or downloading these attachments can infect your computer's hard disk.
Option B) Outgoing Email - This option is incorrect. Outgoing emails don't typically pose a risk of infecting your computer's hard disk with viruses. The risk lies in the attachments or links received through incoming emails.
Option C) CD Roms - This option is incorrect. While it is possible for CD Roms to contain viruses, they are not the most common source of viruses to the hard disk of a computer.
Option D) Websites - This option is incorrect. While websites can sometimes contain malicious code or links that can infect your computer, they are not the most common source of viruses in comparison to incoming emails.
Option E) Mobile - This option is incorrect. Mobile devices, such as smartphones, can be a source of viruses, but they do not directly infect the hard disk of a computer.
The correct answer is A) Incoming Email. This option is correct because incoming emails often carry attachments or links that may contain viruses, making it the most common source of viruses to the hard disk of a computer.