氧瓶燃烧法
参考答案：氧瓶燃烧法：将有机物放在充满氧气的燃烧瓶中进行燃烧，待燃烧产物被吸收入吸收液后，再用适宜的分析方法来测定元素含量的方法。
He thought that painting copied by a modern artist was ______ great value and bought it ____ over a thousand dollars.
A．at; for
B．of; for
C．of; at
D．for; by
铸件为什么会变形？怎样防止？
