单项选择题What is revered as the soul of culture and spirit of Zhangjiajie and reputed as Number One Miraculous Mountain in Western Hunan? A、Tianzi Mountain B、Huangshi Village C、 Hengshan Mountain in Hunan D、 Tianmen Mountain
单项选择题图示为偏置曲柄滑块机构。 试判断该机构是否存在死点位置? A、存在 B、不存在 C、有时存在 D、无法判定