[Taka]

The sentences:

Some of the foundation work for a more just, sustainable future has a very high profile, ringing resonantly in the fine speeches of the world leaders, advocated passionately by the massed groups of environmental and development organizations, amplified with increasing authority by the world's media. Despite the media's tendency to leap from one fashionable cause to the next (from world hunger to AIDS to the environment), it would be narrow-minded to deny their part in increasing environmental awareness. It is easier to be "green" today than ever before.
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Now, what is the topic sentence?

IMO, it's "Some of the foundation work for a more just, sustainable future has a very high profile," (and the conclusion is "It is easier to be "green" today than ever before"). But the problem is, it's not really A SENTENCE: it's part of a sentence, followed by participles.

Is it OK to teach my students that part of a sentence can be also called "topic sentence"?