Solids have definite shape and definite volume. This is because the particles that build up a solid are crammed in a fixed, closely packed geometric arrangement.
Fluids (gases or liquids) do not have definite shape and occupies the shape of the containers. While gases assume the volume of the container, liquids occupy part of it.
In aqueous solutions, the particles lose their shape and volume and occupies the shape of its solvent (water). The volume is also modified accordingly.
Thus, among the given options, CO2(s) has definite shape and definite volume. Correct option is 4.