New technologies have allowed buildings to become taller and heavier than ever before. This is an example of:
A. green design.
B. the engineering process.
C. the evolution of building techniques.
D. material failure.

C. the evolution of building techniques

Hope this helps.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.