需加入适当氧化剂才能实现的反应的

A．PCl₃PCl₅

B．MnO₂Mn²⁺

C．SO₃SO₂

D．Fe³⁺Fe²⁺

—________ the population of the U.S.A. in 2005?

—It ______ about 296 million.

A. What is; is             B. What was; was          C. How many was; was