Sentence Correction

Although the pigeons are widespread, control of them is important in places where their dropping start attracting rats.

(A). the pigeons are widespread, control of them is important in places where their droppings start attracting
(B). widespread, ways to control the pigeons are important in places where their droppings start attracting
(C). widespread, pigeon control is important in places where their droppings start attracting
(D). the pigeons are widespread, control of these is important in places where their droppings start attracting
(E). the pigeons are widespread, their control is important in places where their droppings start attracting

OA is E
What is the OA expression about this sentence? Is it really correct? I need an Expert view on this. Thanks