从起源看，国家是[ ]

A．为全民谋福利的机构

B．阶级矛盾不可调和的产物

C．调和阶级矛盾的工具

One of the     _of our planet's being warming up is an increase in the number of natural disasters.      

[ ]

A. reasons                        

B. causes        

C. result s                                    

D. consequences