在下面的横线上填入正确的单词。

①Thirteen plus ____ equals twenty-five.

② ____ plus eight equals forty-eight.

③Forty-five plus fifty-five equals ____.

④Twenty-four plus ____ equals eighty-two.

⑤Eight plus two equals ____.

—Yesterday , my father bought me a new mobile phone as a present , but I don't know how to use it. 

—Why not read the ________ first before using it ?

下列物质间的转化不能一步完成的是（）