Consider the three points P1(1, 2, 0), P2(3, 6, 20) and P3(2, 4, 6) and a view…

Key idea: a point can obscure another from the viewpoint only if both points lie exactly on the same ray from the viewpoint and one lies between the viewpoint and the other.

• Compute direction vectors from the viewpoint C(0,0,-10):

  C→P1 = P1 − C = (1, 2, 0) − (0, 0, −10) = (1, 2, 10).

  C→P2 = (3, 6, 20) − (0, 0, −10) = (3, 6, 30).

  C→P3 = (2, 4, 6) − (0, 0, −10) = (2, 4, 16).

• Check collinearity and ordering along rays:

  C→P2 = 3 × C→P1 (since (3,6,30) = 3·(1,2,10)), so P2 lies on the same ray as P1 but farther from C. Therefore P1 is between C and P2 and will obscure P2 when viewed from C.

  C→P3 is not a scalar multiple of C→P1 or C→P2 (the ratios are inconsistent), so P3 is not collinear with P1 or P2 and thus cannot obscure or be obscured by them along the same ray.

• Conclusions:

  P1 obscures P2 when viewed from C (true).

  P2 obscures P1 when viewed from C (false).

  P3 does not obscure P1 when viewed from C (true).

  P2 does not obscure P3 when viewed from C (true).

• Therefore, the true statements are: "P1 obscure P2, if viewed from C.", "P3 does not obscure P1, if viewed from C.", and "P2 does not obscure P3, if viewed from C."

Final answer: the correct combination is the three true statements listed above (P1 obscures P2; P3 does not obscure P1; P2 does not obscure P3).