I have no idea what the essay is but if I had to guess, it's the last bubble. It sounds the most like a main idea for the essay
One ton of rocks and one ton of feathers weigh the same. The word that makes both weights the same is the word ton. The weight measurement of ton has a specific number. What differs is if we count the number of feathers and number of rocks to achieve a one ton weight, there's a lesser number of rocks compared to feathers because a rock is always heavier than a feather.
<span>Depending on the work you are discussing, it could refer to the fact that when an author uses words it is for a common purpose or theme in the work.
For example, "damp and brown" are not the most flattering words which the author could use. Therefore, it more than likely is implying a darker more depressing tone. </span>