燃气管道及设施禁止拉绳挂物的原因是会使燃气管道移位、受损、歪斜而造成断裂、漏气，引发火灾、爆炸等事故。()

A. The population of interracial Americans will be three times in 2050 as much as now.
B. There will be no dominant races in America.
C. The divisiveness of the nation is an inevitable problem to confront.
D. At least 50 percent of the third-generation African Americans will marry other ethnic groups.

A. Because it can replace the traditional museum in the near future.
Because it only allows the doctorates to see works that need particular protection.
C. Because when displaying the artworks, it also prevents others from stealing them.
D. Because it almost eliminates the contradiction between displaying and preserving artworks.