be able to可和有生命的主语甚至与无生命的主语连用：I have not been able to write for several days—G. Vidal, 1955; a yarn about not being able to keep a job—K. Amis, 1978;By his proceeding to the beach ... the next phase of the attack was able to proceed—New Yorker, 1986赋予无生命主语以能力,并不总是可取的,如果所接的动词不定式是被动的,那句子就很勉强：No evidence that an air rifle was able to be fired— Times (heading of Law Report), 1988.总体上,最好用情态动词can/could 加被动式,或者把句子写成主动的形式【题】That mistake is ____ corrected.