Answer:
B. Spearman
Explanation:
Charles Spearman was a psychologist who proposed a theory of intelligence. According to him, there's a general factor (the g factor) that can be defined as the overall mental capacity of a person and that it's shown when this person performs cognitive tasks.
According to him, there are no different types of intelligence but just a general factor that determines the "intelligence" of a person and, by determining the value of this factor we could determine one person mental capacities.
Unlike the other authors given in the option, he is the <u>only one</u> who thinks there's a <u>single factor behind intelligence measures </u>(Thurstone believed there were different mental abilities, Gardner proposed the theory of multiple intelligences and Sternberg thought that there were 3 types of intelligence)
Therefore, we can conclude that Spearman would have been the most enthusiastic about the value of a single intelligence test score as an index of an individual's mental capacities.