Sound energy is produced by vibrating objects.
Example: when you speak you vibrate the air molecules in the air. If you where to speak in space no “sound” would be produced since there is nothing for the vibration of your voice to travel through.
Answer : The correct option is, (a) Synthesis
Explanation :
Synthesis reaction : A chemical reaction where multiple substances or reactants combine to form a single product.
It is represented as,

Combustion reaction : A chemical reaction in which a hydrocarbon react with the oxygen to give product as carbon dioxide and water.
It is represented as,

Single replacement reaction : A chemical reaction in which the more reactive element replace the less reactive element.
It is represented as,

In this reaction, A is more reactive element and B is less reactive element.
Double replacement reaction : It is a type of chemical reaction where a positive cation and a negative anion of two reactants exchange places to form two new products.
It is represented as,

(X and A are the cations, Y and B are the anions)
The given reaction is, 
In this reaction, calcium combine with the chloride to form calcium chloride as a product.
Hence, the given type of reaction is a synthesis reaction.
Answer:
Explanation:
a ) false.
NH₃ is more polar molecule than PH₃ so inter-molucular attraction is greater in NH₃ ( hydrogen bond ) . Hence vapour pressure is low for NH₃ .
b ) false .
The average kinetic energy of boiling water molecules is lower on a mountaintop than it is at sea level. It is so because water boils at lower temperture on mountain and kinetic energy of molecules depends upon temperature .
c ) false
vapour pressure depends upon temperature .
d ) True
CCl4 is more volatile than CBr4
e ) false
vapour pressure increases as temperature increases.
The original sample was a compound because it was composed of two different elements and was not purely one element
Answer:
cells -> tissues -> organs -> organ system