一课一题一语法：新概念英语第2册第43课
Hello，大家好！欢迎来到“新概念英语的教与学”！我是上海时学教育的张老师。下面是我们每周一课一题一语法的分享时间，先来公布上一期课后一题的答案。
上一期分享的文章，点击这里回看
下面我们继续本周《新概念英语2》第43课的重点句型或语法的分享。先来读一读课文：
一、课文原文
Lesson 43 Over the South Pole
In 1929, three years after his flight over the North Pole, the American explorer, R. E. Byrd, successfully flew over the South Pole for the first time. Though, at first, Byrd and his men were able to take a great many photographs of the mountains that lay below, they soon ran into serious trouble. At one point, it seemed certain that their plane would crash. It could only get over the mountains if it rose to 10,000 feet. Byrd at once ordered his men to throw out two heavy food sacks. The plane was then able to rise and it cleared the mountains by 400 feet. 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. The aircraft was able to fly over the endless white plains without difficulty.
——选自《新概念英语》第二册，外语教学与研究出版社，1997年10月第1版
二、重点句型或语法
本课侧重区分can与be able to的用法。
1. can 表示“能够或可以”，can的过去时是could。如：
He can speak English and French.
他会讲英语和法语。
I couldn’t understand him.
我无法理解他。
2. 可以用can’t表示否定猜测，如：
That can’t be true.
那不可能是真的。
He can’t be at home.
他不可能在家。
3. be able to表示“能”，有各种时态的变化。如：
Will you be able to come tomorrow?
你明天能来吗？
He is able to swim.
他会游泳。
He was able to swim across the river.
他得以游泳过河。
4. 当要表明一个动作已经成功地完成，必须使用was able to，而不能使用could. 如：
I was able to leave France before the war began.
我能在战争开始前离开法国。
He didn’t agree with me at first but I was able to persuade him.
他开始不同意我的观点，但我最终说服了他。
三、一课一题
根据本课的重要语法点，让我们来练一练吧，请选择正确的选项。
He said he had lost his passport and hadn’t ___ leave the county.