LONDON, Sept 8 (Reuters) - A look at valuations illustrates how regulatory concerns and stubbornly low energy prices have stoked investor anxiety over Royal Dutch Shell (Xetra: R6C1.DE - news ) 's planned takeover of British rival BG Group (LSE: BG.L - news ) .
In the context of the input sentence, determine the relationship between 'BG Group' and 'Royal Dutch Shell'.
Options: stock exchange, developer, chairperson, parent organization