Can you explain question 1?

Sure. It was:

            To use Bootstrap, at minimum your page needs to load
                (check all that apply)
            A. An HTML file
            B. A CSS file
            C. A JavaScript file
            D. A jQuery file

The answer is B, because the JS part of Bootstrap is optional

A fair number of people included an HTML file, but our pages don't load HTML files. (They are HTML files, but they don't typically load them.)

What does the sm mean in class="col-sm-3"?

Great question. Bootstrap has so many classes that naming is a real challenge.

What it means:

col → this is a grid column
sm → applies starting at the small breakpoint
3 → the column takes up 3 out of 12 grid columns

Breakpoints:

    | Prefix | Screen width |
| ------ | ------------ |
| (none) | < 576px      |
| `sm`   | ≥ 576px      |
| `md`   | ≥ 768px      |
| `lg`   | ≥ 992px      |
| `xl`   | ≥ 1200px     |

I don't have questions at the moment. Thank you! / Currently no, thanks! / No question this time!

Great!