Questions

The receptor molecules, which receive signals from outside the cell, passing the signal to the inside.

In order for a nerve cell, or any cell, to perceive its environment, it needs a sensory apparatus. And for an individual cell, most of that sensation is derived at the cell surface. So, it expresses on its cell surface proteins that span across the membrane.

In the outside world, these proteins can act to receive signals, catching molecules on the outside and then as the molecule passes to the inside of the cell, they can send signals like alarm signals that can tell the cell that a particular molecule is outside.

Hence, here B is the receptor cell.

Hospitality actually means, taking care of guests in the best possible way.

Organizing, providing services and looking care after guests is included in it.

It means friendly and generous treatment of guests. 

Hospitality industry includes all companies involved in providing services for guests. They provide more mental satisfaction than tangible objects.

A Secret is what you want to share if you have with you. And if you share that secret with anyone, then secret will not be with you only.

Chloroform, CHCl3 is easily oxidised to the highly poisonous gas known as phosgene or carbonyl chloride COCl2. Hence if it is used as anaesthetic it should be kept free from sunlight and air.

The persons with 'O' blood group do not have antigens in the red corpuscles. So that blood will not cause agglutination of corpuscles if mixed with any type of blood. So group 'O' persons are called universal donors.

An up - selling is getting the customer to spend more money, buy a more expensive model of the same type of product, or add features or warranties that relate to the product viewed or purchased. 

A cross - sell is to get the customer to spend more money by adding more products from other categories than the product being viewed or purchased.