Challenge 3: Comparing With/Without a Mask Without Risking It — Solution Walkthrough

The correct approach:

Disable the mask temporarily — shift-clicking its thumbnail, or the
equivalent action in either tool — rather than deleting it.

Why, per this chapter's own warning box:

Deleting a mask permanently discards it, usually with a prompt asking
whether to apply its current effect or discard it outright — either
way, the mask itself is gone afterward, and any careful work put into
building it would need to be redone from scratch if it turned out to
still be needed. Disabling the mask instead temporarily ignores its
effect entirely, showing the image exactly as it would look without
the mask, while leaving the actual mask data completely intact and
unchanged underneath.

Why this specifically solves the comparison problem:

Disabling can be toggled back on just as easily as it was toggled
off, letting you switch freely between "with mask" and "without mask"
views as many times as needed to make a real comparison — something
deleting the mask would make impossible without rebuilding it entirely
from scratch each time.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise directly applies this chapter's own disable-vs-delete
distinction to the exact comparison scenario the warning box was
written to address, correctly recommending the fully reversible option
over the permanent one.