Which question is focused and answerable enough to be considered an effective research question?

Question

Is immigration a positive thing?
Who benefited most from the Immigration and Nationality Act of 1965?
How many immigrants gained US citizenship?
How many Chinese immigrants live in the US?

Answer 1

The research question that is focused and answerable enough to be considered effective is: "Who benefited most from the Immigration and Nationality Act of 1965?"

This question is clear, specific, and allows for analysis of the effects of a particular piece of legislation on specific groups, making it suitable for a research project. The other questions, while they may be interesting, are either too broad or not clearly focused on a specific researchable aspect.