Frozen co2 or dry ice is different from co2 gas in the atmosphere because it has
a. no mass
b. a fixed shape
c. a lower density
d. no fixed volume

Option (b) is the correct answer.

Explanation:

Dry ice is the solid form of carbon dioxide whereas carbon dioxide gas present in the atmosphere is present in gaseous phase.

Also it is known that in solids,  particles are held together tightly due to strong intermolecular forces of attraction. As a result, solid substances have fixed shape and volume.

On the other hand, in gases particles are held by weak intermolecular forces due to which they are far apart from each other. As a result, they do not hace any fixed shape.

Hence, we can conclude that frozen or dry ice is different from gas in the atmosphere because it has a fixed shape.

the answer your looking for is c).