Questions

In music, a fugue is a contrapuntal compositional technique in two or more voices, built on a subject that is introduced at the beginning in imitation and which recurs frequently in the course of the composition. 

Hence, the main theme of a fugue is called the subject.

An invention that improved safety for railway passengers is Air brakes. With the use of air brakes using compressed air, become more effective by preventing many train accidents.

Amazon, is an American electronic commerce and cloud computing company.

Payment gateways process credit card payments and other forms of internet transactions, in a secured format via any website or web-enabled device. They facilitate these transactions by transferring critical information between payment portals and the front-end processor, which is usually a bank.

Amazon uses its own payment gateway Amazon Pay Payment gateway.

Energy tranfer takes place either by means of Heat or Work only in Thermodynamics.

Heat :: Heat Energy is defined as Energy that can be transferred due to temperature change.

Whereas

Thermal Energy :: Thermal Energy is the Internal Energy stored in the system maintained at a certain Temperature.

An ideal habitat with unlimited resources is associated with Exponential growth.

Special Friend - Stone.

Example ::

He is my special friend - He is my stone.