Let ( l₁ ) be the line through the origin and the point ( (s2, 0, 21d) ). Let ( l₂ ) be the line through the points ( (s1, 21, 1d) ) and ( (s4, 1, 3d) ). Find the distance between ( l₁ ) and ( l₂ ).
a) ( √(s1² + s2² + s4²) )
b) ( √(s1² + s2² + s4² + 1) )
c) ( √(s1² + s2² + s4² - 1) )
d) ( √(s1² + s2² + s4² + 4) )