Final answer:
Scuba diving tanks and cans of fly spray require compressed gas to function effectively. Without compression, a scuba tank wouldn't have enough air for diving, and a fly spray can would not expel its contents effectively.
Step-by-step explanation:
If Scuba diving tanks did not contain compressed gas or if cans of fly spray were not pressurized, they would not work effectively (option b). Scuba diving tanks need compressed air to provide a sufficient amount of gas that a diver can breathe underwater. The compression allows a large volume of gas to be stored in a small, portable tank. Fly spray cans work on the same principle, where the pressurized contents are released as a fine mist when the nozzle is activated.
Without compression in scuba tanks, there would not be enough air for the diver to breathe for more than a few breaths, which would quickly end the dive and could potentially be very dangerous. Similarly, if a fly spray can weren't pressurized, the contents would not be expelled from the can effectively, making the product useless. In both cases, the physics of compressibility and the necessity for pressure are crucial for the functionality of the devices.