参考答案：B

解析：

[分析]： 语义的理解和判断。 根据原文I made him jump to a steep slope below．He skidded in the winter mud to the edge of the slope and hung for an instant，balanced dangerously，half falling into the deep valley hundreds of feet below．Miraculously，he got his footing again可知，说者策马向下面的陡坡跳，马在坡边的冬泥里打滑，坚持了片刻，勉强保持平衡，向下面几百英尺深的峡谷落去，奇迹发生了，它站住了。由此可见，B项说法与原文相符，该项是正确答案。[解题关键] 正确定位相关信息处，并理解表示系列动作的词语含义。