The thick fog made it impossible for the plane to land.

The thick fog made it impossible for the plane to land.

• A. The plane could land as the fog was hardly thick.
• B. The plane cannot land because the fog is thick.
• C. It was possible for the plane to land although the fog was thick.
• D. The plane was unable to land because of the thick fog.

The answer is D. The plane was unable to land because of the thick fog.

The other answer choices are all incorrect because they imply that the plane could have landed, even though the fog was thick. The only correct answer is D, which states that the fog made it impossible for the plane to land.