Here's a LearnAPphysics.com problem of the day. (I'll attach it immediately after this post.) The issue is that the wording is somewhat vague. Here's my questions:

Where actually is the point charge in choice (c)? Is it inside the interior surface of the hollow cubic shell, is it inside the shell itself, or is it outside the external surface of the shell? If either of the latter two is true, then I see how (c) is false.

I would have thought that choice (d) is true. When it says, "just above the surface of the cube," would "1 meter above the surface of the cube" mean the same thing

Question

Here's a LearnAPphysics.com problem of the day.  (I'll attach it immediately after this post.)  The issue is that the wording is somewhat vague.  Here's my questions:

Where actually is the point charge in choice (c)?  Is it inside the interior surface of the hollow cubic shell, is it inside the shell itself, or is it outside the external surface of the shell?  If either of the latter two is true, then I see how (c) is false.
 
I would have thought that choice (d) is true.  When it says, "just above the surface of the cube," would "1 meter above the surface of the cube" mean the same thing

underhill · Answer

(Attached is the LearnAPPhysics problem.)

underhill · Answer

Here's a link to the official solution: http://www.learnapphysics.com/solution.php?pc=0c9978ef5d7f6ed9c64dfbb26bb80fbe

turingtest · Answer

I see what you mean about the vagueness. For C I interpreted the point to be just outside the cube, so that would be wrong.
D might be approximately true, for a very large cube if we are very close to the surface. Since the face of the cube has edges though I don't think this is a safe assumption. 
As far as if 1m is close enough, we are not given the size of the cube. However the choice is that the E-field is constant, not approximately constant, so this is not such a great answer.
The only one that is true regardless of the size of the cube, or any other scaling issue you may consider is B. So though it may not be a perfectly well-written question, I still agree with the answer.

underhill · Answer

When you say "constant," do you mean that the EF is changing relative to a fixed point, or that the EF changes as you move closer to or further away from the cubic shell?

turingtest · Answer

that if changes as you move
that the EF is not a constant magnitude and direction throughout space

obviously for any static charge the resulting EF will not be changing at a fixed point

turingtest · Answer

that it changes*

underhill · Answer

Ah, I see.  You have just cleared up a number of uncertainties I've had while studing EM.  When I read "constant EF" in the past, I've always thought that meant relative to a fixed point!  The solution makes good sense now.  Thanks, TT.

turingtest · Answer

welcome!