Correct option is D
According to the given statement,
Conclusion I: This follows, because it is clearly given that if a poor man has ability he can earn wealth.
Conclusion II: This does not follow, nothing is given about wealthy man.
Conclusion III: This also does not follow, because it is not mentioned in the statement that a poor man is always able.
Conclusion IV: This does not follow, because it is not mentioned in the statement.
Hence, "only conclusion I" follows.