题目

 完形填空     In learning English, one should first pay attention to listening and speaking. It is the ground work of reading and writing. You’d better   1   your best to speak while you do much listening.      Don't be  2   of making mistakes.But be careful not to let them stop you from improving your   3  . While you are doing this, a good   4  is to write---keep a diary, write notes or letters.  Then if you can, ask some others to go through   5  you have written and tell you where there is a mistake. Many mistakes in your speaking will be   6   found wh在△ABC中，AD为∠A的平分线，请用正弦定理证明：。