1.Please sing this song（ in）Chinese.请用中文唱一下这首歌.
2.Let's begin our class (with)an interesting song.让我们用一首有趣的歌曲开始这堂课吧.
3.You'd better think of a problem ( in ) a positive way.你最好用正确的方式来看待这个问题.
4.She is surprised （at ）the beautiful scenery.她惊叹于那美丽的风景.
5.The brave man likes fiying ( on ) an airplane.那个勇敢的男人喜欢乘飞机.ps:by跟交通工具间一般没有任何成分.故应用on.
6.I used to be (in) the soccer team.
我曾是足球队的一员.