The deadman's zone in the blast furnace consists of

The deadman's zone in a blast furnace refers to the central region at the bottom of the furnace where the burden materials slow down and become relatively stagnant.

This zone is composed primarily of a closely packed column of coke that remains largely stationary while the surrounding materials continue to descend.

The coke in this region supports the overlying burden and provides permeability for the upward flow of gases.

It is called the "deadman" because of its limited movement compared to other parts of the furnace burden.

Therefore, Option C is correct as the deadman zone consists mainly of coke only.