Splits reduce the doors on haulage roads but increase number of . . . . . . . .

A. $$\frac{1}{R} = \frac{1}{{{R_1}}} + \frac{1}{{{R_2}}} + \frac{1}{{{R_3}}}\,.\,.\,.\,.\,.\,\frac{1}{{{R_n}}}$$

B. $$\frac{1}{{\sqrt R }} = \frac{1}{{\sqrt {{R_1}} }} - \frac{1}{{\sqrt {{R_2}} }} - \frac{1}{{\sqrt {{R_3}} }}\,.\,.\,.\,.\,.\, - \frac{1}{{\sqrt {{R_n}} }}$$

C. $$\frac{1}{{\sqrt R }} = \frac{1}{{\sqrt {{R_1}} }} + \frac{1}{{\sqrt {{R_2}} }} + \frac{1}{{\sqrt {{R_3}} }}\,.\,.\,.\,.\,.\,\frac{1}{{\sqrt {{R_n}} }}$$

D. $$\frac{1}{{\sqrt R }} = \sqrt {{R_1}} + \sqrt {{R_2}} + \sqrt {{R_3}} \,.\,.\,.\,.\,.\,\sqrt {{R_n}} $$

Answer: Option C