Questions

Because the refractive index of glass is highest, light travels slowly in Glass. 

We know that the speed of light depends on the refraction index. The higher the index of refraction is, the slower the speed of light is.

R.I of air and vacuum = 0 (air is a teeny bit more but can be taken as 0)
R.I of water = 1.33
R.I of glass = 1.4.

Hence, Light travels slowest in Glass.

If as a business, you buy goods or services on credit from a supplier (accounts payable) then the supplier will supply the goods and business will incur a liability to the supplier for that amount, but no cash will change hands at that stage.

Some of those shop keepers allowed regular "trustworthy" customers to purchase items without having the full payment.

Hence, Buying on credit means that no actual money has changed hands.

A Dome-shaped, muscular and membranous structure that separates as a partition of the thoracic and abdominal cavities is Diaphragm. 

Thoracic or chest cavity ::  It is the cavity where the heart and lungs are present. It is the second largest hallow space in the body.It also has vertebral column, ribs, breast bone,...

Abdominal cavity :: It is the cavity where the digestive tract, liver, kidneys, the spleen, pancreas,... are located. It is the largest hallow space of the body.

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

 Don’t take it to heart : Mind, the client is not angry with you, they are displeased with the work of your product or for showing the quality of service that you provide. Your personal emotions are beside the factor.

  Find a solution: Once you understand why the purchaser is unhappy, it is time to provide a solution. Ask him what he feels should be completed or put forward your own truthful and realistic solution to the problem. In maximum cases, that’s all the customer is searching out —and may bring about  providing some degree of satisfaction.