In the figure shown `S_(1)O-S_(2)O=S_(3)O-S_(2)O=(lambda)/(4)`, Intensity at O due to any one of the slits is `I_(0)`. What is the intensity due to all the three coherent sources `S_(1), S_(2) and S_(3)` ?
A. `3I_(0)`
B. `I_(0)`
C. `5I_(0)`
D. `9I_(0)`