1. The plane of a cube cannot be:
(1) an obtuse triangle; (2) a right triangle; (3) a rhombus; (4) a regular pentagon; (5) a regular hexagon.
The correct option is ( ).
(A)(1)(2)(5)
(B)(1)(4)
(C)(2)(3)(4)
(D)(3)(4)(5)
(The cross-section of a cube can be an acute triangle, isosceles triangle, equilateral triangle, but it cannot be an obtuse triangle or a right triangle; for quadrilaterals, it can be an isosceles trapezoid, parallelogram, rhombus, rectangle, but it cannot be a right trapezoid; for pentagons, it can be any pentagon, but it cannot be a regular pentagon; for hexagons, it can be a regular hexagon. Answer: (B).)