Is gas pressure increasing a physical or chemical change?

In chemistry, there are two major types of change. As stated here, the physical change and the chemical change. 

To clearly differentiate these two,

Physical change happens when only the physical characteristics of the substance are changed. These physical characteristics includes the shape, mass, among others.

Chemical change happens when there is a production of new chemical that is brought about by the reaction. 

In this item, the increase in pressure only affects that physical property of the system. Hence, the answer should be PHYSICAL.

The correct answer should be "electrons orbit the nucleus in circular motions exactly as shown on the classic bohr model."

C, small, hard spheres with insignificant volumes