Answer:
Any medium solid, liquid or gas is required for sound waves to travel.
Explanation:
A sound wave requires a medium to travel. Sound waves are mechanical waves that is why these waves require a medium to travel. Sound waves can travel through solids, liquids, and gases.
In solids, the particles of the medium are closely packed together as compared to liquids and gases. In liquids, particles are less tightly packed and almost negligible in gases.
Therefore sound waves produce vibration in the dense or solid medium. Denser the medium faster the sound waves travel. However sound waves can not travel through empty space.
The balanced equation of the combustion of the propane is

From the above chemical equation, it is clear that 1 mole of propane requires 5 moles of oxygen to undergo complete combustion as the result of this reaction, 3 moles of carbon-di-oxide and 4 moles of water molecules will be produced.
Therefore one-half mole of propane requires 2.5 moles of oxygen to undergo complete combustion. And in the reaction, 1.5 moles of carbon-di-oxide and 2 moles of water molecules are produced.
Therefore the answer is, 'One-half of propane combines with 2.5 moles of oxygen to produce 2 moles of water and 1.5 moles of carbon dioxide'
Answer: The correct answer for the fill in the blank is - medium of exchange.
Explanation-
When we use paper money to pay for food, the money is a medium of exchange as we are exchanging our money with their food. So, it plays a role of medium of exchange in purchasing our food.
On the other hand, unit of account is also a feature of money but it only indicates the price of food at which we are purchasing it. Store of value is used when we store our money as a wealth, then it becomes store of value .
Hence, medium of exchange is the correct answer.
Answer:
Base units are defined units based on specific objects or events in the physical world. Derived units are defined by combining base units.
Base units are defined by a particular process of measuring a base quantity whereas derived units are defined as algebraic combinations of base units. For example, length is a base quantity in both SI and the English system, but the meter is a base unit in the SI system only.
Explanation: A sneaker is a want because you don't actually need it to survive