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一、选择题(本大题共12小题,每小题5分,共60分,在每小题给出的四个选项中,只有一项是符合题目要求的.)1.已知下列命题(其中a,b为直线,α为平面):①若一条直线垂直于一个平面内无数条直线,则这条直线与这个平面垂直;②若一条直线平行于一个平面,则垂直于这条直线的直线必垂直于这个平面;③若a∥α,b⊥α,则a⊥b;④若a⊥b,则过b有惟一一个平面α与a垂直.上述四个命题中,真命题是()A.①②B.②③C.②④D.③④
First, the multiple-choice questions (the title of a total of 12 small questions, each question 5 points, a total of 60 points, in each question given four options, only one is in line with the requirements of the title.) 1. Know the following Proposition (where a, b is a straight line, and α is a plane): 1 If a line is perpendicular to an infinite number of lines in a plane, the line is perpendicular to this plane; 2 if a line is parallel to a plane, then perpendicular to this one The straight line must be perpendicular to this plane; 3 if a ∥ α, b ⊥ α, then a ⊥ b; 4 if a ⊥ b, then b has the only plane α perpendicular to a. The above four propositions, true propositions Yes () A.12B.23C.24D.34