题目内容：

为什么用would be able to ,如果用was able to 可以吗
Byrd now knew that he would be able to reach the South Pole which was 300 miles away,for there were no more mountains in sight.

优质解答

对 to reach the South Pole 这件事 在细微层次的理解和潜在的信息是不同的.比如一个人在几年前要去做1件事 和一个人在几年前做了/做过1件事的概念是不同的.在此,to reach the South Pole 这件事,在当时（几年前）是...