The oceanic crust is composed mainly of diabase, gabbro, and

a. basalt.

b. quartz.

c. obsidian.

d. aquamarine.

The oceanic crust has three layers; layer 1, layer 2 and layer 3. Layer 1 consists f unconsolidated or semiconsolidated sediments. It contains of land sediments. Layer 2 is divided into two parts; uppermost volcanic layer and finely crystalline basalt. It s thin in the mid ocean but thickens away from the ridge. The third layer consists of coarse grained gabbros and igneous rocks that have a low content of silica rocks. It also consists of diabase dikes. So the answer is letter A.

The oceanic crust is composed mainly of diabase, gabbro, and basalt.