Receiver of Wreck is an official of the British government whose main task was to process incoming reports of shipwrecks so as to give legitimate owners the opportunity of retrieving their property and ensure that law abiding finders of wreck receive an appropriate reward

A. was to process incoming reports of shipwrecks so as to give legitimate owners the opportunity of retrieving their property and ensure that law-abiding finders of wreck receive
B. had been processing of incoming reports of shipwrecks in order to give legitimate owners the opportunity to retrieve their property and ensuring that law-abiding finders of wreck receive
C. has been to process incoming reports of shipwrecks so as to give legitimate owners the opportunity for retrieval of their property and for ensuring that law-abiding finders of wreck received
D. is to process incoming reports of shipwrecks so as to give legitimate owners the opportunity to retrieve their property and ensure that law-abiding finders of wreck received
E. is to process incoming reports of shipwrecks in order to give legitimate owners the opportunity to retrieve their property and ensure that law-abiding finders of wreck receive

Non underlined uses present tense so A,B and C gone. Between D and E , E wins as receive is the correct tense and not received.