`He went` vs `He has gone` （过去时

    A: Is Mr. Bob at home?
    B: Sorry, he isn't at home. He___to Hong Kong for vacation?

        A. went
        B. has gone
        C. is going

过去时，表示过去发生，暗示现在已经结束。
现在完成时，表示过去发生，现在或将来仍有可能继续。

所以，答案是 B。

参考资料

1. https://english.stackexchange.com/questions/139550/what-is-the-difference-between-has-gone-and-went-in-this-context
2. https://www.quora.com/What-is-the-difference-between-%E2%80%9Che-went%E2%80%9D-and-%E2%80%9Che-has-gone%E2%80%9D