be able to能作谓语动词
句子中be able to do 是谓语
be able to 是情态动词,与后面的动词一起构成谓语。
如:
1、He is able to swim . (主谓结构)
( 谓语:is able to swim)
他会游泳。
2、 He is able to speak English . (主谓宾结构)
( 谓语:is able to speak)
他会说英语。
词性是动词短语,例如:
1、I doubt they'll be able to help but it's worth a try.我不敢肯定他们能够帮得上忙,但不妨试一试。
2、He should be able to lead a perfectly normal life.他应该能够过上完全正常的生活。
3、I have some information you may be able to use.我有些可能对你有用的信息。
这是一个系表结构,意为“能够做…”。例如,Finally, he was able to speak English smoothly. 终于,他能流利地说英语了。