【判断题】勾股定理证明中,赵爽“出入相补”的做法与欧几里德添辅助线的做法比较,赵爽证法直观易懂,欧几里德证法较为抽象。
【单选题】The underlined word 'precarious' in the third paragraph means ______.
【单选题】线性规划无有限最优解的判别条件为:( )
【简答题】The payment procedure starts when the B/E is handed in on condition that it is not refused.