不定冠詞a和an的例句

1． 表示“一”這個數量概念,比one意思稍弱 e.g.:The plan will be ready in a week or two.
2． 表示某人或某物,但不具體說明哪個,相當于any e.g.:This poem was written by a student.注：在1,2兩項中,如果名詞變復...