Consider a third box surrounding a third region of space.

$$ For the third time, we can$$t see into the box, but we know that the electric field points into

the box on the left, and an equal electric field points out of the box on the right.

$$ Evaluate the kind of charge that must exist inside the box:

A$.$ Negative charge.

B$.$ Neutral charge.

C$.$ Positive charge.

D$.$ No charge.

E$.$ Impossible to tell.