“三硬”厚煤层指的是顶板坚硬、底板坚硬、煤质硬度f≈4。（）
参考答案：对
—I’ve heard a hurricane had struck your hometown.
—Yes, it was terrible, but ____, no one was killed.
A．sadly
B．unfortunately
C．hopefully
D．fortunately
曲线的铅直渐近线方程为（）。
的铅直渐近线方程为（）。