Final answer:
The presence of clam shells within the rock sample would best support the student's hypothesis that the rock was formed from ocean floor sediments, as marine fossils are strong indicators of a rock's origins in ocean environments.
Step-by-step explanation:
The best evidence to support the student's hypothesis that the rock sample formed from ocean floor sediments would be D. Clam shells found within the rock sample. If the rock is sedimentary and contains marine fossils like clam shells, it strongly suggests that the rock formed in an ocean environment. Marine fossils are excellent indicators that the sediments from which the rock was formed accumulated on the seafloor. Comparatively, a textbook (Option A) could provide general information about rock formation, but it would not provide direct evidence about the specific rock sample. A suite of rock samples from various locations (Option B) could provide a broader context but not necessarily support the specific hypothesis unless those samples also contain marine fossils. Option C, a model of different crustal plate boundaries, would help understand the tectonic settings but not directly prove the sedimentary origin of the rock sample.
The presence of clam shells within the rock would be consistent with the rock being formed from marine sediments, as suggested by the student's hypothesis. This aligns with knowledge of sedimentary rocks being formed in various environments, including marine settings where organisms with shells live and die. The combination of their hypothesized origin, marine fossils, and the fact that the Valley & Ridge region of Virginia has a geological history involving the uplift and exposure of oceanic materials, would strongly support the student's hypothesis.