43. Why is the geometric structure of a molecule
important, especially for biological molecules?

Structure is particularly important for biological molecules because a slight change in the structure of a large bio molecules like nucleic acids, proteins, enzymes, carbohydrates and lipid molecules can completely destroy its usefulness to a cell and may even change the cell from a normal one to a cancerous one.

Combustion is the act or process of burning. therefore, i believe the answer is  a: burning wood. 

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.