Which combination of elements would form an ionic bond? Oxygen and sulfur
fluorine and iron
calcium and sodium
carbon and bromine

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.

im doing test rn im going with 2 but ill give answer if itss wrong,   : )