1、can do : take pictures because China have many amazingly breathtaking sceneries.
myriad delicious foods
go to historical museum because China is one of the four oldest countries.
can not do :somethings which violate laws and harm for the society.
smoking in the public places and make noise in here.

2 Personally, I'm for extensive travel and I do think students should travel during their holidays if they don't have anything more important to do.
The advantages of extensive travel vary denpending on different people. For me, it gives me an opportunity to discover a world partly or totally different from what i am accustomed to. I get to meet different people, know different cultures and of course, see different sceneries. This experience broadens my mind and enables me to realize, this world is so big and full of varieties. Each of these varieties needs my understanding and deserves my respect. This is one of the ways a young person learns how to be patient and tolerant.
The disadvantages of extensive travel, from my view point, is that it's energy and money consuming. I need a good rest after an extensive travel. It's not as people often think a good rest from work or study.One last point I would make is, extensive travel is not suitable for any student. Some students lack the ability to feel or discover the abundantness of another culture thus extensive travel ends to be a waste of money and time.
3.mankind should observe laws which relate to genetic engineering
do not intendtionally disturb nature .