单项选择题 由3 个结点可以构造出多少种不同的有向树?(北方交通) A、2 B、3 C、4 D、5

判断题 The procedure used in the partial-pivoting Gaussian elimination does not change the value of the determinant, and the sign of the determinant, which can be fixed with the knowledge of the order of pivoting elements.

判断题 慢说朗诵,即便日常说话,当进入特殊的情感时,声音也会自然带出一些特征,客观地强化语言的表达。