①将植物细胞置于较高浓度的蔗糖溶液中，发生质壁分离的是活细胞；

②观察用健那绿染色的口腔上皮细胞，发现线粒体被染成蓝绿色，则口腔上皮细胞是死细胞；

③将好氧细菌与水绵一起制成临时装片，用极细的光束照射水绵，若发现细菌没有趋向水绵照光部位，则说明细菌可能为死细胞；

④洋葱根尖经解离后，若发现细胞被龙胆紫溶液染上了色，则表明根尖细胞在解离前已死亡．

   Volunteering means that you work to help people without being paid. There are many different volunteers. They help people who really need help. There are many places where you can be volunteers. Here are just a few places for you.
   Hospital---ask if you can go and visit people who are really sick. Sometimes what they need is someone to talk to, or someone to give them hope.
   Orphanage (孤儿院) ---the children living there really need someone to play with them.
   Food Shelter---many food shelters need people to clean up the shelters and help give out food or water to those who need it.
Home for the elderly ---help the elderly people clean up their homes.
   Community (社区) Center ---a lot of community centers are very well run. However, some of them really need extra help, especially cleaning and repairs.
   As a student you can also do a lot of things to help others at school. Maybe you could start a support group.
   Here is some advice:
   Help students give up smoking, drinking or other bad habits.
   Help students who come from poor families.
   Help new students get used to their school life soon.
   Provide seniors with information on future studies.