Explanation:
If keys are in the wrong hands, documents will be able to be read regardless of where they are on the network. Choice A is incorrect because firewalls can be perfectly configured, but if the keys make it to the other side, they will not prevent the document from being decrypted. Choice B is incorrect because even easy encryption algorithms require adequate resources to break, whereas encryption keys can be easily used. Choice C is incorrect because the application “front door” controls may be bypassed by accessing data directly.