Analyze the relationship between 'BG Group' and 'Royal Dutch Shell' within the context of the input sentence.
Options: publisher, position held, headquarters location, parent organization

LONDON, Sept 2 (Reuters) - Royal Dutch Shell (Xetra: R6C1.DE - news ) gained EU approval on Wednesday for its $58 billion acquisition of Britain's BG Group (LSE: BG.L - news ) , the second of four key markets needed to clear the deal, but faced a slight delay in securing a decision in Australia.
parent organization