The elements of a group have the same number of in their
shell.
A outer
B. electrons
c. inner
D. protons

B

Explanation:

electron.elements of the same group have the same electrons

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.