Answer:
Option (D)
Explanation:
Ravenstein was the person who published many laws from the year 1876 to 1889. According to him, an individual migrates to large distance of about 5000 miles or more, form various reasons. This may include unemployment problems, for higher and better education, affected by natural disasters such as floods, earthquakes, and droughts.
They mostly travel to the economically powerful country because economically stable and powerful countries can provide job facilities, education, and other services, which an economically weaker country cannot provide.
Thus, the correct answer is option (D).