[单选题]粘液质的高级神经活动类型的基本特征是( )。
A. 强、平衡、不灵活
B. 弱
C. 强、平衡、灵活
D. 强、不平衡
E. 弱、平衡、灵活

At the Kyoto conference on global warming in December 1997, it became abundantly clear how complex it has become to work out international agreements relating to the environment because of economic concerns unique to each country. It is no longer enough to try to forbid certain activities or to reduce emissions of certain substances. The global challenge of the interlink between the environment and development increasingly bring us to the core of the economic life of states. During the late 1980s we were able, through international agreements, to make deep cuts in emissions harmful to the ozone layer (臭氧层). These reductions were made possible because substitutions had been found for many of the harmful chemicals and, more important, because the harmful substances could be replaced without negative effects on employment and the economies of states.
Although the threat of global warming has been known to the world for decades and all countries and leaders agree that we need
A. the leaders of many countries are not fully aware of the gravity of the problem
B. world technology is not able to solve the problem
C. not all the countries are willing to make deep cuts in emissions
D. many people welcome the global-warming effect of a warmer summer