Questions

The two main components of air are nitrogen and oxygen. They are seperated by the fractional distillation of liquid air. Liquefied air contains liquid nitrogen and liquid oxygen. Liquid nitrogen with the lower boiling point more readily evaporates than the less volatile liquid oxygen. 

Office salaries expense would not come under a selling expense.

Any of the basic mechanical devices for applying a force are called simple machines.

There are 6 basic simple machines; the lever, the wheel and axle, the inclined plane, the wedge, the pulley, and the screw. Several of these simple machines are related to each other. But, each has a specific purpose in the world of doing work.

Controlled railroad crossing includes warning signs, red lights and railway gates, whereas absence of all of these warning signs like red lights and gates includes uncontrolled railroad crossings. 

Tips : 

The leader's role is :

To communicate the strategic vision to management with clarity

 To translate the vision into concrete direction and plans

To identify and communicate priorities, short term objectives, timelines, performance measures, clear accountabilities and performance agreements to management;

 To provide quality judgment and advice.