Explanation
Popular services such as iCloud, Dropbox, and OneDrive are all publicly available and are open to any user for free, with possible add-on services offered for a cost.

Explanation
An intrusion detection system (IDS) is implemented to watch network traffic and operations, using predefined criteria or signatures, and alert administrators if anything suspect is found. An intrusion prevention system (IPS) is similar to an IDS but actually takes action against suspect traffic, whereas an IDS just alerts when it finds anything suspect. A firewall works at the network level and only takes into account IP addresses, ports, and protocols; it does not inspect the traffic for patterns or content. A web application firewall (WAF) works at the application layer and provides additional security via proxying, filtering service requests, or blocking based on additional factors such as the client and requests.

A retina scan could be used in conjunction with an RSA token because it is a biometric factor, and thus a different type of factor. An access card, RFID, and USB thumb drive are all items in possession of a user, the same as an RSA token, and as such would not be appropriate.