下列关于东北三省的说法，正确的有（    ）

  ①位于北方地区的东北部

  ②包括黑龙江省、吉林省和辽宁省

  ③小兴安岭主要位于黑龙江省

  ④小兴安岭位于黑龙江和松花江之间

填空 根据句子意思，用所给单词的适当形式填空，将答案写在答卷上。
⑴Can you imagine his ____ (walk) on the moon?
⑵The little girl____ (prefer) the red one and her mother bought it for her at last.
⑶Can you ____ (memory) all the words in one week?
⑷The cat's ____ (die) brought the whole family much sorrow.
⑸You ought to pay attention to ____ (listen) to the teacher carefully in class and be more careful not to make any stupid mistake..
⑹She remembered____ (close) the windows, but when she came back she found them all ____ (open).
⑺Finally she finished the tough work by herself ____ (success).
⑻Nowadays a great number of ____ (woman doctor) are very successful .
⑼ I am used to____ (send) her e-mails instead of____ (write) letters.
⑽Unless Tina ____ (study) harder from now on, she____ (fail) the exam.