Evidence about Dalton's atomic theory has shown that A. all of Dalton's hypotheses were correct.
B. atoms of an element can have different numbers of protons.
C. atoms are divisible.
D. all atoms of an element are not identical but they must all have the same mass.

a graduated cylinder.

explanation:

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.