Why does the author mention refrigeration in paragraph 6? A．To show how the steam engine contributed to refrigeration B．To illustrate the standard of living of North America and Europe C．To give an example of an innovation that expanded markets D．To argue that refrigeration was the most important invention of the time
A.To B.To C.To D.To
【参考答案】
C 解析：The author's purpose is to give an example of an in......