What is the definition of plane (in math) a) a location in space with no length, width or depth. b) a collection of at least 2 points, arranged in a straight path. c) points that lie on the same line. d) a flat surface with infinite, length, width, but no thickness.

The correct answer is the option D.
 The definition of plane is: a flat surface with infinite, length, width, but no thickness. 
 So, by this concept, we can know that a plane is bidimensional. How can we know it is bidimensional? Well, we know that it has no thickness, but length and width, so if a body is projected with lenght and widht, we say that it has two dimensions, but If this object also had depth, it would have three dimensions.