This question is very confusingly worded, but I think your best answer is C. Let's break it down:
A is most likely wrong, since Gautama didn't exactly say Hindus were "destined" to unhappiness (after al,l he proposes a path to happiness that could be followed by anyone—even Hindus). And Buddhism retains many of the Hindu scriptures (called Vedas) in its own tradition.
B is definitely wrong because we have no record of Gautama ever journeying to Cambodia, and Gautama could not have "adopted" Buddhism there because Buddhism didn't exist yet (since it was founded by Gautama himself).
C is tricky, but it's the least-bad answer. Gautama did encounter a Hindu monk who persuaded him to renounce material wealth and live a live of poverty as an ascetic. BUT when Gautama tried this out, he found that this method didn't end lead to enlightenment after all. He therefore abandoned asceticism and began looking for a new path to happiness. That path later became what we know as Buddhism. So yes, Gautama's encounter with the monk at first convinced him that Hindu-style asceticism was the path to enlightenment, but Gautama's decision to pursue a new path to happiness resulted from his disillusionment with the monk's path.
D is absolutely wrong because Gautama had no relationship to Judaism whatsoever, and may not even have known that Judaism existed.