Concept:The angle between two lines is found using their direction vectors. If the dot product of these vectors is zero, the lines are perpendicular.Explanation:For the first line, let 3x=2y=−z=k.Then x=3k, y=2k, z=−k.So its direction vector is proportional to (31,21,−1), which simplifies to (2,3,−6).For the second line, let −x=6y=−4z=m.Then x=−m, y=6m, z=−4m.So its direction vector is proportional to (−1,61,−41), which simplifies to (−12,2,−3).Now take the dot product: (2,3,−6)⋅(−12,2,−3)=−24+6+18=0.Since the dot product is zero, the direction vectors are perpendicular.Therefore, the angle between the lines is 2π.Answer:Option C: 2π