The BEST way of characterizing what sociologists currently believe about upward social mobility for any individual is that it is the result of .

The effort of individuals and society ( and it's public policy) that enable it

Explanation:

The BEST way of characterizing what sociologists currently believe about upward social mobility for any individual is that it is the result of

Social mobility refers to the movement of an individual or groups in social position over time i.e the movement of individual from one social position into another. When an individual improve or decrease their economic status  in a way that affects their social class, as a result of this an individual can experience upward or downward social mobility.

Upward social mobility is said to occur  when an individual class is higher than that of his or her parents i.e the capacity for rising to a higher social or economic position

sounds good to me mate!