Final answer:
The type of fault where trees become closer is likely a reverse or thrust fault, both involving upward movement of the hanging wall due to compressional forces. The correct option is B.
Step-by-step explanation:
When two trees that were formerly side by side become closer after faulting, the type of fault involved is likely a reverse fault or a thrust fault.
Both of these faults are characterized by the hanging wall moving upwards relative to the footwall, due to compressional forces.
However, it's important to distinguish them based on the angle of dip: a reverse fault has a steep angle, whereas a thrust fault has a gentle dip of less than 30°.
In the scenario described, where trees become closer, it suggests a shortening of the Earth's crust, which aligns with the description of a reverse or thrust fault, both resulting from compression. The correct option is B.