ANS:A - counter current reactor

A blast furnace is typically considered a counter-current reactor. In a blast furnace, the reactants (iron ore, coke, and limestone) are introduced at the top, while hot air is blown into the bottom of the furnace. As the reactants move downward through the furnace, they come into contact with the rising hot gases, creating a counter-current flow. This allows for efficient heat transfer and chemical reactions to occur, leading to the reduction of iron ore and the production of molten iron.