IMO answer should be A
Rejecting the idea that space must be the representation of a relation or a substance, Immanuel Kant understood that space is instead an integral entity inherent to the systematic structure that allows humans to comprehend and arrange events.
A. of a relation or a substance, Immanuel Kant understood that space is instead an integral entity inherent to................Looks fine
B. of a relation or substance, Immanuel Kant understood that space is instead an integral entity inherent with......................Parallelism error. 'Inherent to' is preferred
C. of a relation or a substance, space, according to Immanuel Kant's understanding, is instead an integral entity inherent to...........................Rejecting the idea phrase should modify Immanuel Kant. In this option, Space is wrongly being modified.
D. as a relation or a substance, Immanuel Kant understood instead that space is an integral entity inherent to.....................................'Representation of' is preferred. Meaning issue as well.
E. of a relation or substance, space, as Immanuel Kant understood it, is instead an integral entity inherent to.............................'Space' is being modified instead of Immanuel Kant