Read the following introductory paragraph:

Summer is here at last, a time when many people are happily stepping out to enjoy the fresh air and sunshine. However, there is a cloud on the horizon. There is another cloud in front of that doorway, and yet another cloud hovering around an outdoor caf$.$ Unfortunately, these clouds are not natural; they are the result of a personal habit that negatively impacts others. With cigarette smoke in the air, people cannot enjoy the scent of flowers and freshly cut grass. With cigarette butts littering streets and parks, children can no longer run barefoot through the grass. It is time to ban smoking in all outdoor public spaces.

What is the main function of the sentence "Unfortunately, these clouds are not natural; they are the result of a personal habit that negatively impacts others" in the paragraph?

It introduces the topic $/$ provides background information.

It presents the thesis.

It hooks the reader.

It helps set the tone.