Questions

We can say that sales promotion is a cost effective technique by which an organisation can achieve its sales volume or the marketing objectives by providing value added product and not just an ordinary product to the end user or even the intermediaries. It is short term by nature and is suitable enough for generating sales within a short span of time. Sales promotion techniques are being increasingly used by retailing organisations some of which include advertising, providing discounts and allowances or a 'buy one get one free offer' etc.

A restrictive clause is one that limits the meaning of the word it describes.

For example :: 

The girl who lives next door is beautiful.

This restrictive clause limits "the girl" to say it's specifically the one next door.

A respirometer is a device used to measure the rate of respiration of a living organism by measuring its rate of exchange of oxygen and/or carbon dioxide.

The number of protons is equal to the number of electrons. That is the number of positive charges is equal to the number of negative charges.