C.poisonous substance, which can't be used in overcrowded areas

　　D.fuel, which is stored in large tanks

　　5.From the discussion among some experts we may coclude that ____.

　　A.to avoid any accidents we should not repair the facilities in chemical industry

　　B.the local authorities should not be concerned with the production of the chemical industry

　　C.all these accidents could have been avoided or controlled if effective measure had been taken

　　D.natural gas stored in very large tanks is always safe

　　第十一篇答案：DBABC