To answer the question "Which points are coplanar?" based on the image, we need to identify the points that lie on the same plane.

In the diagram:

• Two planes are shown, one vertical and one horizontal.
• The points labeled in the question include $A$, $B$, $C$, $E$, $H$, and $M$.
• Coplanar points are those that all lie on the same plane, either the vertical or horizontal one.

From the image, it is clear that:

• Points $A$, $B$, $C$, and $E$ lie on the horizontal plane.
• Points $H$, $M$, and $B$ lie on the vertical plane.

Therefore, the coplanar points on the horizontal plane are $A$, $B$, $C$, and $E$.

Would you like more details or have any further questions?

Here are some related questions to expand on this:

1. What defines coplanar points in geometry?
2. Can points be coplanar if they are not on the same physical plane in a diagram?
3. How do you determine if points in 3D space are coplanar using coordinates?
4. What is the difference between collinear and coplanar points?
5. Can three points in space always be considered coplanar?

Tip: When solving coplanar problems, visualize or sketch planes and highlight points to see which ones lie on the same flat surface.