Two light rods AB = a + b, CD = a - b are symmetrically lying on a horizontal plane. They are kept intact by two strings AC and BD. The perpendicular distance between the rods is 'a'. The length of AC is given by

Options

A. a
B. b
C. `sqrt (a ^(2) - b ^(2))`
D. `sqrt (a ^(2) +b ^(2))`