although the driver was badly hurt,he____exlpain what had happened.A wasable to B.couldI'm sorry,Mrs.Smith.I've broken your glasses.It doesn't matter,Mark,but you____careful.A.must be B.should have been

although the driver was badly hurt,he____exlpain what had happened.A wasable to B.couldI'm sorry,Mrs.Smith.I've broken your glasses.It doesn't matter,Mark,but you____careful.A.must be B.should have been
although the driver was badly hurt,he____exlpain what had happened.
A wasable to B.could
I'm sorry,Mrs.Smith.I've broken your glasses.
It doesn't matter,Mark,but you____careful.
A.must be B.should have been

although the driver was badly hurt,he____exlpain what had happened.A wasable to B.couldI'm sorry,Mrs.Smith.I've broken your glasses.It doesn't matter,Mark,but you____careful.A.must be B.should have been
although the driver was badly hurt,he____exlpain what had happened.
A wasable to B.could
选A
was able to 表示过去“能做”并且“做到了”
could仅表示过去“能做”
根据上下文,在本句中显然是强调“能并且做到了”因此选A
I'm sorry,Mrs.Smith.I've broken your glasses.
It doesn't matter,Mark,but you____careful.
A.must be B.should have been
选B
should have+过去分词是情态动词should的用法之一,用来表示,轻微的责备.
汉语常常译为“你本该.”（实际上没有）
整句话可译为：
没关系,马克,但是你本该小心一点的.

选A
你可以比较下can和be able to的用法
1）can could 表示能力；可能 (过去时用could),
只用于现在式和过去式(could)。
be able to可以用于各种时态。
如：They will be able to tell you the news soon.
他很快就能告诉你消息了。
2）只用be ab...

全部展开

选A
你可以比较下can和be able to的用法
1）can could 表示能力；可能 (过去时用could),
只用于现在式和过去式(could)。
be able to可以用于各种时态。
如：They will be able to tell you the news soon.
他很快就能告诉你消息了。
2）只用be able to 的情况：
a. 位于助动词后。
b. 情态动词后。
c. 表示过去某时刻动作时。
d. 用于句首表示条件。
e. 表示成功地做了某事时，只能用was/were able to， 不能用could。
如：He was able to flee Europe before the war broke out.
= He managed to flee Europe before the war broke out.
补充的问题选B
should have done 表示本应该....，但是没有做到！
这句翻译：没关系，但是你可以小心一点的（暗指可以避免发生）

收起

B
was able to表示某种能力，即某人在某一具体场合做某事的能力，往往暗示经过努力才具备的能力
could表示能够的意思

即使这司机受伤很厉害，但他还是能够解释当时发生的一切
（整个动作都是发生在过去，所以用了过去式）
指【过去某时或某个时刻】设法做成某事，不用could,而用was\were able to
综上，选A