Step 1: Understanding the Concept:
The question asks to identify the economist associated with the "welfare-oriented" definition of economics, which shifted the focus from mere wealth to human welfare.
Step 2: Detailed Explanation:
Different economists have defined economics from different perspectives:
\begin{itemize}
\item Adam Smith gave a wealth-oriented definition, defining economics as "an inquiry into the nature and causes of the wealth of nations."
\item Alfred Marshall provided the welfare-oriented definition. In his book "Principles of Economics" (1890), he defined economics as "a study of mankind in the ordinary business of life; it examines that part of individual and social action which is most closely connected with the attainment and with the use of the material requisites of well-being."
\item Lionel Robbins gave a scarcity-oriented definition, defining economics as "the science which studies human behaviour as a relationship between ends and scarce means which have alternative uses."
\end{itemize}
Marshall's definition is distinctly focused on human welfare as the central subject of economics.
Step 3: Final Answer:
The welfare-oriented definition of Economics was given by Alfred Marshall. Therefore, option (B) is the correct answer.