We have to identify the statement about the plane which is not true.
1. Consider the first statement,
" A plane can be thought of as flat". It is true as plane is a flat surface.
2. Consider the second statement,
"The surface of a plane is made up of points". It is true as plane is a flat surface which is made up of points.
3. Consider the third statement,
"A plane can be seen". It is not true as plane is a flat surface which can not be seen.
4. Consider the fourth statement,
"A plane extends infinitely in all directions". It is true as plane is a flat surface that extends infinitely along its edges.