关于语法笔记上的细节2个问题 can/be able to

crack25

1.can和be able to的区别:

You can say that somebody is able to do something, but can is more usual.

Bau can has only two forms: can and could. So sometimes it is necessary to use be able to.

For instance: I will be able to get the car in a week.

就是说不需要从意思上（能力还是可能性）加以区分，只要注意时态和对称的角度看哪个更合适就行。

**: can和be able to在与主语搭配逻辑上没有问题的情况下(如主语都是”人”，而不是物)，可以平行。

笔记上说的这个，从时态角度区分，感觉有些不明白，时态是想说如果 could 和is able to这两个出现的话，要根据原句的时态来判断吗？可是could 也可以出现在一般时中吧！！。这个涂蓝的地方到底想说什么？
谢谢各位

crack25

224. (GWD-12-Q13)
Although energy prices have tripled in the United States over the last two years, research indicates few people to have significantly reduced the amount of driving they do, nor are they making fuel efficiency a priority when shopping for cars.
A.    few people to have significantly reduced the amount of driving they do, nor are they making
B.    few people having significantly reduced the amount of driving they do or made
C.    that there are few people who have significantly reduced the amount of driving they do, nor having made
D.    that few people have significantly reduced the amount of driving they do and are not making
E.    that few people have significantly reduced the amount of driving they do or made


其实这个题目做对了，就是一看笔记纠结了，已经是否定含义了不需要再有nor，只要用or就好；这个怎么会这样说？因为lili语法笔记说了，or是必须用在否定句，否定含义不等于否定句，我非常确定这一点，所以我从逻辑上能判断出用or，但是这个否定含义，我认为和赵丽语法冲突了。。。表示不理解，求证

crack25

恩，好吧，自己痛苦着，来顶