If the trapezoid below is reflected across the x-axis, what are the coordinates
of B?
A. (4-8)
B.(-4,-8)
C. (-4,8)
D. ( -8,-4)

As you may have intentionally forgotten to add the diagram. The diagram of the trapezoid is attached below.

The point B(4, 8) after reflection across x-axis would be B'(4, -8).

B(4, 8)        →       B'(4, 8)  

Step-by-step explanation:

The rule of reflection across the x-axis states that a reflection of a point, let say M(x, y), across the x-axis does not change the value of x-coordinate but changes the sign of the y-coordinate of the point.

In a nutshell,

The point M(x, y) after reflection across x-axis would be M'(x, -y)

M(x, y)        →       M'(x, -y)

From the diagram attached below, the coordinate of point B is (4, 8).

So, according to the rule of reflection across the x-axis, the coordinates of the image of the point B (4, 8) after the reflection across the x-axis will be B'(4, -8).

i.e.

The point B(4, 8) after reflection across x-axis would be B'(4, -8).

B(4, 8)        →       B'(4, 8)