[最佳答案] C 本题考查can和be able to的差别。 ① can和be able to都可以表示有能力作某事,但be able to的主语必须是人或动物,而can 没有这个限制,如: He can swim. =" He" is able to swim. The radio can be fixed in 30 minutes.(句中的can不能用be able to) ② 根据be动词的变化而有各种时态的变化,而can只有过去时。 ③ be able to表示克服困难或通过努力做成某事,其过去时可表示"设法做成",相当于managed to do或succeeded in doing,而can表示本身具有能力做某事。如: With the help of the firemen, they were able to leave the burning house. 本题是指通过节省房钱来攒钱,当然用be able to更合适,再如: Although his leg was hurt, he was able to swim to the bank.