A(n) ________ is a foreign key in one table that does not have a matching value in the primary key field of a related table

A user receives a phone call from a person claiming to be from tech support. This person knows the user's name and that the user has Windows installed on their computer. The technician directs the user to open Event Viewer and look at some event log entries to demonstrate the effects of a virus on the computer. The technician also asks the user for their user ID and password so that they can clean the computer. This is an example of which of the following security threats?

a. Malware b. Phishing c. Virus d. Social engineering

What are some of the common causes of boot failures?

What will be an ideal response?