The answer to this question is <span>Longitudinal Study
The main purpose of this type of study is to find out whether a certain variable will give different response if the time factor is change.
Examples of this time of study would be: a sudy to find out how long it need for a certain viruss to develop if it got injected since early age.</span>
They must be over 30 years old, must live in the state they want to represent, and must be a us citizen for 9 years
Is it just a bill, like a water or gas bill?
Answer: There are 21 countries that have Spanish as an official language. Those countries are… Mexico is the biggest Spanish speaking country with the most Spanish speakers in the world. While Spanish is an official language of the country it is not the only one.
Explanation: Hope this helps :)
