当气体压力不变时，它的体积和温度的变化为（）。
A、直线变化
B、常数
C、曲线变化
D、不确定
参考答案：A
Though lacking money and support from his family, he ________ to complete the task by himself,
which brought him confidence and experience.[ ]
A. tried
B. attempted
C. ran
D. managed
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