Answer:
15. True
16. False
17. True
18. False
19. True
20. False
21. True
Step-by-step explanation:
15. The three points can be taken as being two points on a line adjacent to a point which always forms a plain when the ends of the line are connected to the point
16. The two circles can be on different planes
17. With one line fixed, the other line can be rotated until both lines are in the flat plane
18. The definition of skew lines are lines in different planes that are not parallel and that do not intersect
19. Whereby the angle crosses the circumference of the circle twice, the number of intersections = 4
20. Two distinct circles can only intersect twice
21. A plane can always be drawn with any three points
