Challenge 1: Selecting and Moving an Entire Flat Surface at Once — Solution Walkthrough

The answer:

Per this chapter's own material, Face Select mode achieves this most
directly. Switching to Face Select lets a click target the entire flat
surface as one selectable unit, rather than needing to select each of
its four corner vertices individually.

Why Vertex Select would be a less direct approach here:

Selecting the four corner vertices individually in Vertex Select mode
would technically move the same overall surface if all four are moved
together, but it requires selecting each point separately first and
risks accidentally missing one or selecting an extra, unrelated vertex
nearby.

Why Face Select fits this specific task:

Per this chapter's own material, Face Select mode is built specifically
for treating a filled surface as one selectable, movable unit — exactly
the "select and move an entire flat surface at once" requirement
described here, without needing to think about the individual vertices
or edges that make it up.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise checks that a whole-surface selection and move is
correctly matched to Face Select mode, rather than the more granular
Vertex Select mode.