A sentence putting an idea into operation for development in an essay is the Thesis Statement.
Explanation:
When starting an essay:
various notes are made of ideas that pop up in the writer´s mind.
These are logically organized and the chosen idea is what will grab the reader´s attention.
The next stage is to describe this attention grabber in a few sentences. These 2 or 3 sentences will be concluded with a Thesis Statement. The Thesis Statement reveals how the writer intends to argue the position he /she intends to take in the development of the essay.
Explanation: The children are clearly smiling (a sign of happiness) while reading the books. They're enjoying it. Also, I took the test and got it correct.
