Which of the following could be considered a security risk during boarding?

A person without a boarding pass attempting to enter the gate area is indeed a security risk during boarding because they do not have authorized access to the secure area of the airport. Boarding passes serve as a means to verify that a passenger has gone through security checks and is cleared to enter the boarding area. Allowing individuals who do not have the necessary credentials could lead to unauthorized access to secure areas of the airport, which can compromise the safety of passengers, crew, and the aircraft itself.

In contrast, a passenger carrying a backpack is not inherently a security threat; many travelers carry bags for legitimate reasons. A family traveling together is also typical and does not pose a risk unless their behavior raises concern. Similarly, crew members showing their IDs are following protocol and are authorized personnel, thus not presenting a security risk.