Which statement best describes how an existing theory is often affected by the development of new technology? An existing theory is thrown out and replaced with a completely new theory based on the new observations.
An existing theory is modified so that it can explain both the old and new observations.
An existing theory remains the same because a theory is a proven fact that is always true.
An existing theory is kept unchanged while a new theory is developed to explain the new observations.

16- counting by fours

Following are the  advantages of the parametric equations: 1) they can be used to graph curves that are not functions, like the unit circle.2) the parameter can be used to represent the quantity that is  useful to  provide us with better information about the graph.3)  it is useful to convert between rectangular equations and parametric equations.with specific reference to chemistry,  parametric equations are employ for solving hydrogen and hydrogen-like ions, quantum mechanically. herein, cartesian coordinates are converted in spherical polar coordinates. the solution obtained, when plotted on spherical polar graph paper, provides visualization of atomic orbital such as s,p,d and f. 

Ibelieve the answer is balance! hope my answer has you : )