Answer:
d. Some magma generated during seafloor spreading spills out to produce a new layer of seafloor called gabbro.
Step-by-step explanation:
- The magma is spilled from the mid-oceanic ridges and spreads onto the seafloor creating a newer seafloor.
- This is why it's called as the divergent boundary due to the spreading of magma on both sides of the floor. Grabbo is a coarse-grained mafic intrusive igneous rock and is formed at the oceanic ridges.