In the context of the input sentence, determine the relationship between 'BG Group' and 'Royal Dutch Shell'.
Options: stock exchange, member of, parent organization, chief executive officer

Merger and acquisition activity in the energy sector has been rekindled as company valuations slumped along with oil prices, highlighted by Royal Dutch Shell (Xetra: R6C1.DE - news ) 's $70 billion bid to acquire BG Group (LSE: BG.L - news ) earlier this year.
parent organization