Final answer:
Scarps on Mercury are unique linear cliffs formed from the planet's crust wrinkling as it shrank, signifying a type of tectonic activity different from Earth's plate tectonics.
Step-by-step explanation:
What is unique about scarps in the context of Mercury's tectonic deformation? The correct answer is b. Linear cliffs or escarpments. Unlike Earth where tectonic activity is caused by plate movements, Mercury exhibits a different form of tectonic feature. These long, curved cliffs known as scarps are evidence of compression in Mercury's crust. This compression and resultant wrinkling likely occurred as the planet cooled and shrank, crumpling the crust and creating these scarps. Significantly, these scarps cut across pre-existing craters, indicating that they formed after those impacts had already shaped Mercury's surface.