Concept:The Earth’s crust consists of an upper lighter layer called sial and a lower denser layer called sima, which forms the ocean floor.
Explanation:The lithosphere includes the crust and the uppermost part of the mantle.
The continental crust is made of lighter rocks known as sial, rich in silica and aluminium.
The oceanic crust is made of denser rocks known as sima, rich in silica and magnesium.
Sima lies below the continents and also forms the floor of the oceans.
Therefore, the part of the lithosphere that makes up the ocean floor is sima, not nikel or nife.
Answer:B. sima