Our teachers are really . They often work in their office far into the night.A. open-minde

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A. open-minded
(答案→)B. hard-working
C. self-confident
D. warm-hearted
解析：考查词义辨析。open-minded心胸开阔的，hard-working 勤劳的，self-confident 自信的，warm-hearted 热心肠的，句意：我们真得很勤劳。他经常在办公室工作到深夜。所以选B。