Cell membranes contain a central bilayer formed by:

Lipids

Explanation:

The cell membranes are primarily made up of two layers. The central bilayer is formed by the lipids in the cell membrane. Lipids surround the cytoplasm of cells to help the cell control substances that go in and out of the cell. This helps to protect the cell from a harmful substance that may potentially enter the cell.

(Some information from "StaceeLichtenstein" on )

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the oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf, but operationally is often referred to as beginning where the water depths drop to below 100 meters (328 feet), seaward from the coast to the open ocean.

explanation:

a and c are the answeres