Questions

Sound is a kind of energy created when something vibrates. When this vibration reaches an ear, it is translated into what we recognize as a sound. Sound vibration must travel through matter. Therefore, it can travel through air and water but not through vacuum.

‘Suppose’ and ‘if’ both are used to guess, or think, or imagine something and both means the same thing. So, using them together is superfluous. So, ‘if’will be used. 

The regional rural bank is not allowed to trade in over-night borrowing market.Scheduled commercial banks (excluding RRBs), co-operative banks (other than Land Development Banks) and Primary Dealers (PDs), are permitted to participate in call/notice money market both as borrowers and lenders.Overnight borrowing market, also known as call market, generally involves borrowing and lending of funds for one day and generally takes place against government securities.

Everyone has special skills; some people use them very well is the sentence which is correctly punctuated.