Which of the following is not evidence of sea-floor spreading? a. the alternation of polarity in segments of the ocean floor b. the relationship between earthquakes and plate boundaries c. analysis of seafloor sediments d. the distribution of ice sheets across the planet

The answer is D (the distribution of ice sheets across the planet)

Explanation:

Seafloor spreading is a geomorphic process where there is a slow accumulation of new oceanic crust in the ocean floor through a volcanic action while moving the older rocks away from the mid-oceanic ridge. The mid-ocean ridge is located where the seafloor spreading process occurs, in which tectonic plates divide from one another.The theory of Seafloor spreading was proposed by an American geophysicist, Harry H. Hess in 1960. Another theory named “The Continental Drift” of Alfred Wegener in 1912 is supported by this hypothesis on the shift position of the earth’s surface.

Sea Floor Spreading Evidence

Harry Hess’s hypothesis about seafloor spreading had collected several pieces of evidence to support the theory.  

Molten materialSeafloor drillRadiometric age dating and fossil agesMagnetic stripes

So, the distribution of ice sheets across the planet is not evidence of sea-floor spreading.

Learn more:

Relationship between plate tectonics and "seafloor spreading linkTypical rate of seafloor spreading. link

Keywords: seafloor spreading, geomorphic process, molten material, magnetic strips, hypothesis

A,b,c is the answer to the question

I'm pretty sure it's c. extremely gradual but not 100% sure though.