做新多益閱讀大全時，時態的章節有特別提到:
現在進行式(be +Ving)的形式也是表現未來預定的事或是將要發生的事
請問如下練習題，為什麼不能選(A)呢？
選現在進行式？
Mr. Sanders __(B)___ out of the country until next Friday, but you can contact him by e-mail if there are matters of urgency.
(A) is being
(B) will be
(C) will have been
(D) has been
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