Which evidence originally supported Hess’s idea of seafloor spreading in 1968?

Question

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.

Answer 1

The evidence that originally supported Harry Hess's idea of seafloor spreading in 1968 was:

Younger rocks are closer to mid-ocean ridges.

Hess proposed that as new oceanic crust is formed at mid-ocean ridges, it pushes older crust away from the ridge, which leads to the observation that the youngest rocks are found nearest to these ridges, while the older rocks are found farther away. This concept was crucial in supporting the theory of seafloor spreading.