Final answer:
The correct answer to the question is (c) low, slower, because sound travels slower in air than in denser media due to air's higher compressibility and lower rigidity.
Step-by-step explanation:
The question relates to the concept of impedance in the context of sound travelling through different media. The impedance of air is low, meaning that it is less resistant to the passage of sound waves compared to more dense materials. However, just having low impedance does not necessarily mean sound will travel faster. Instead, sound travels faster through media that are less compressible and more rigid, despite their density. Sound travels slower in air compared to solids and liquids because air is more compressible. Therefore, the correct answer to the question is:
Examples in the reference material show that sound travels faster in solids like iron than in air, not because of lower mass or equal rigidity, but because solids like iron are much more rigid and less compressible than air. Also, sound travels faster in hydrogen than in air, not because of its density but because hydrogen atoms are lighter than air molecules, which allows sound energy to be transferred more easily.