Which of the following is an example of biological mechanical action (or weathering? ) a. rocks breaking into smaller pieces due to growing salt crystals in their pores. b. potholes forming on roads when water inside pavement joints freezes and expands. c. the heating and cooling of minerals inside rocks, fracturing them. d. tree roots from a tree next to a sidewalk growing underneath it and uplifting and cracking the sidewalk. e. acid and rain water producing an acidic solution that disintegrates gravestones.