Answer
(a) CO is on the left side, adding it causes a shift to the right ( toward products).
(b) $CO_2$ is on the right side, removing it causes a shift to the right (toward products).
(c) $Fe_3O_4$ is a solid in this reaction, so its concentration do not affect equilibrium.
(d) Dry ice is made of $CO_2$ molecules. $CO_2$ is on the right side, adding it causes a shift to the left (toward reactants).
Work Step by Step
According to Le Chatelier's Principle, adding a reactant or a product shifts the equilibrium to the opposite side, and removing some shifts the equilibrium to the same side.
(a) CO is on the left side, adding it causes a shift to the right ( toward products).
(b) $CO_2$ is on the right side, removing it causes a shift to the right (toward products).
(c) $Fe_3O_4$ is a solid in this reaction, so its concentration do not affect equilibrium.
(d) Dry ice is made of $CO_2$ molecules. $CO_2$ is on the right side, adding it causes a shift to the left (toward reactants).