If OA=a, OB=b, OC=c are the co-terminus edges of regular parallelopiped, then the shortest distance between the diagonal and the side OA not meeting the diagonal is
A. `(bc)/sqrt(b^(2) +c^(2))`
B. `(ca)/sqrt(c^(2) +a^(2))`
C. `(ab)/sqrt(a^(2) + b^(2))`
D. `(abc)/sqrt(a^(2) + b^(2) +c^(2))`