You seem to be asking two different questions: a) how to determine terrain elevation on a sectional, and b) what is the correct answer to this FAA test question?
First, there are multiple ways to determine terrain elevation on a sectional, as the FAA's Chart User's Guide says:
Our Aeronautical Information Specialists are devoted to showing the
contour of the earth and any obstructions clearly and accurately on
our charts. We use five different techniques: contour lines, shaded
relief, color tints, obstruction symbols, and Maximum Elevation
In addition to those five things, sectionals also show airport elevations, perennial lake elevations and spot elevations (and maybe others). You can find details of all those things in the Guide.
Second, what's the correct answer to that specific test question? Others have already answered that, but I suspect that the FAA is expecting you to use multiple methods, e.g. use the logic from ymb1's very neat answer, confirmed by looking at obstacle elevations and MEFs. But that's my own speculation, I don't know for sure how they think you should determine the elevation. The main point is just that there are multiple ways to do it, depending on what features and information are on the specific sectional area that you're looking at.