An saturated solution: 1) Is unstable because it has dissolved more solute than would be expected.
2) Has dissolved exactly as much solute as is theoretically possible
3) Hasn’t dissolved as much solute as is theoretically possible

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.

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

i think its 100.

hope this !