Exercise 6 Page 539

The definition of skew lines is that they are neither parallel, coplanar or intersecting. Therefore, the first two statements are false. A.& AB and CD are parallel B.& AB and CD intersect C.& AB and CD are perpendicular D.& A, B, and C are noncollinear Perpendicular lines could be intersecting if they are coplanar. Therefore, we cannot be sure if the third statement is true. A.& AB and CD are parallel B.& AB and CD intersect C.& AB and CD are perpendicular D.& A, B, and C are noncollinear The last statement is, for skew lines, definitely a true statement. If C isn't noncollinear, by definition they must be collinear which means they would not be skew lines. This makes the solution D.