In the context of 'Expectancy Theory', which of the following statements best explains the relationship between effort, performance, and outcomes?

A、Higher effort always guarantees better performance, regardless of the individual's abilities.
B、The motivation to increase effort is influenced by the belief that it will lead to improved performance and desirable outcomes.
C、Outcomes are the only factor that determines an individual's motivation, making effort irrelevant.
D、Performance is solely dependent on the external rewards offered, rather than the individual's effort.