What are coplanar points?
$
 {\text{A}}{\text{. points lying on same line}} \\
 {\text{B}}{\text{. points lying on same axis}} \\
 {\text{C}}{\text{. points lying on same object}} \\
 {\text{D}}{\text{. points lying on same plane}} \\
$

Hint:To solve this question we have to understand the word coplanar and then we will be able to answer whether coplanar points lie on a plane or something else.

Complete step-by-step answer:
We have,
Coplanar points:
Coplanar points are three or more points which all lie in the same plane. Any set of three points in space are coplanar. A set of four points may be coplanar or may not be coplanar.
In other perspective:
In geometry a set of points in space are coplanar if there exists a geometric plane that contains them all. For example three points are always coplanar and if the points are distinct and non collinear the plane they determine is unique.
From above definition we understand that coplanar points means points lying on same plane
Hence option D is the correct option.

Note: - Whenever we get this type of question the key concept of solving this is a question related to vectors and we have to have three dimensional imagination to tackle this type of questions easily.We have to understand the concept and properties of vectors to solve this question.