1. 指出下列句中主语的中心词(中心词指去掉名词中所有冠词，如a，an，the或其他定语和修饰词以后剩下的那个单词，如： The teacher with two of his students is walking into the classroom. 主语的中心词：teatcher） ① There is an old man coming here. （1）____________[br][/br] ② The useful dictionary was given by my mother last year.（2）____________ ③ To do today's homework without the teacher's help is very difficult.（3）____________