What is shown in the image?

The correct answer is B. Sign shows maximum truck clearance height. This is because the image depicts a sign with a horizontal line representing a bridge or overpass and a downward arrow with a number. This type of sign is used to indicate the maximum height a truck or vehicle can be to safely pass under the upcoming bridge or overpass. It is important for drivers to pay attention to these signs to avoid accidents or damage to their vehicles.

Options A, C, and D are not correct as they do not match the image description provided.