_____ is our belief that improvements in health care will lead to a stronger, more prosperous economy. [ ]

A. As

B. That

C. This

D. It

使用二氧化碳灭火器时，二氧化碳液体汽化成气体喷出，覆盖在火焰表面，主要起（）作用。

A、降低温度

B、隔绝空气

C、减少烟雾

D、减缓燃烧