Just Two Communication Theories?

I've been reviewing the "APR Study Guide" in preparation of my upcoming exam. As I finished the section on "Communication Theory," I was surprised to note that only two theories were identified: Agenda-Setting Theory and Diffusion Theory. Brief descriptions follow:

The Agenda-Setting Theory describes a process that is an interplay between three elements: the media, the public, and the policy-makers. At first, it was hypothesized that the media set the agenda, giving the public an issue to advocate for and the policy-makers the approval to legislate. Today, the application of this theory is regarded as multi-dimensional, where any one of the three elements can set the agenda and garner the attention of the remaining two.

The Diffusion Theory examines the sometimes lengthy process of getting humans (creatures of habit) to accept a new idea or product. It uses terms like "word of mouth," "innovators," and "early adopters" to describe its everyday application.

What would my revered professor from Saint Mary's College, Kusum Singh, think of this? I recall an interesting semester spent poring over several different communication theories, challenged by Professor Singh to examine how each played out in our everyday lives. My APR pursuit (back to the PR textbooks) has me looking back fondly on those college years and especially on the classes taught by Professor Singh. I hope she is happy, healthy, and inspiring a new generation of Communications majors at Saint Mary's.