Particles of masses m, 2m, 3m,.............nm grams are placed on the same line at distances \[l,\,2l,\,3l,\,.......nl\]cm from a fixed point. The distance of centre of mass of the particles from the fixed point in centimeters is

• A. \[\frac{(2n+1)l}{3}\]
• B. \[\frac{1}{n+1}\]
• C. \[\frac{n({{n}^{2}}+1)l}{2}\]
• D. \[\frac{2l}{n({{n}^{2}}+1)}\]