Solution:To determine which points obscure others from the viewpoint C, need to calculate the depth of each point relative to C. The depth can be computed using the distance formula.
The smaller the depth value, the closer the point is to the viewer comparing the depth.
1. P1 is closer to C than P2. So, P1 obscure P2 from the viewpoint C.
2. P2 is farther to C than P1. so, P2 does not obscure P1 from the viewpoint C.
3. P3 is closer to C than P1. so, P3 does not obscure P1 from the viewpoint C.
4. P2 is farther to C than P3. so, P2 does not obscure P3 from the viewpoint C.
Thus, the statement (A), (C) and (D) are correct.