Questions

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.

Economics deals primarily with the concept of Scarcity and choice. Scarcity is the limited availability of a commodity, which may be in demand in the market. Scarcity also includes an individual's lack of resources to buy commodities.

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.

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.