The users in your department are accessing their day-to-day applications (and their data) over the
network using a web browser. What type of service are they utilizing?

A.
Software as a Service (SaaS)

B.
Infrastructure as a Service (IaaS)

C.
Data Processing as a Service (DPaaS)

D.
Platform as a Service (PaaS)

Explanation:
http://searchcloudcomputing.techtarget.com/definition/Software-as-a-Service