Question

which evidence originally supported hess’s idea of seafloor spreading in 1968?
○ younger rocks are closer to mid-ocean ridges.
○ the destruction of crust occurs at deep-sea trenches.
○ oceanic rocks are pillow-shaped when formed.
○ rocks across the ocean floor have alternating magnetic stripes.

Explanation:

This magnetic stripe evidence, paired with the known reversal of Earth's magnetic field, directly confirmed that new seafloor was forming at mid-ocean ridges and spreading outward, providing the key original support for Hess's seafloor spreading hypothesis in 1968. The other options are either related observations that were contextualized by seafloor spreading or part of the broader model, not the critical original supporting evidence.

Answer:

D. Rocks across the ocean floor have alternating magnetic stripes.