Final answer:
The substance that will take the shape of its container but not the volume is O₂ gas (Option B), since gases expand or contract to fill a container's available space but do not have a fixed volume.
Step-by-step explanation:
The substance that will take the shape of its container but not its volume is O₂ gas (Option B). This is because gases do not have a fixed shape or volume; they acquire the shape of their container and expand or contract to fill the container's available space. In contrast, liquids, like water (H₂O), have a fixed volume but take the shape of their container.
Solids, such as sodium chloride (NaCl), maintain both a fixed shape and volume and do not conform to their container's shape or volume. Hydrogen gas (H₂), like oxygen gas, is also a gas and will behave similarly, taking the shape of its container.