Which of the following sentences indicates a successful condition linked to hard work?

The choice that best indicates a successful condition linked to hard work is the one stating that he is successful because he works hard. This formulation clearly establishes a direct relationship between hard work and success, highlighting that the individual's achievements are a direct result of their efforts and diligence.

In contrast, the other options convey different narratives. One suggests that success is achieved without effort, while another indicates hard work without subsequent success. The third option mentions hard work and success but does not explicitly connect them causally, as the phrase "although he is very successful" implies that hard work and success coexist but does not confirm that the former leads to the latter. Therefore, the choice that asserts a clear causal link between working hard and achieving success unmistakably reflects the intended message.