I.冠词填空：在下列句中空白处填入适当冠词，不需用冠词处划×。
1.Thereis_______pictureof_______elephanton_______wall.
2.Thisis_______usefulbook.I'vereaditfor_______hour.
3._______elephantismuchheavierthan_______horse.
4._______doctortoldhimtotake_______medicinethreetimes_______day.
5.Let'sgooutfor_______walk.
6.It'stoohot.Open_______door，please.
7.Thereis_______womanoverthere._______womanisMeimei'smother.
8._______sunrisesin_______east.
9._______ChangjiangRiveris_______longestriverin_______China.
10.Areyougoingtodoit_______secondtime?
11.Washingtonis_______capitalof_______USA.