Which of the Following Better Explains 'Buying Centre

Which of the following better explains 'Buying Centre'? 

A)  A buying centre relates to all those individuals and groups who respond to the purchasing decision-making process. 
B)  A buying centre relates to all those individuals and groups who participate in the purchasing decision-making process. 
C)  A buying centre relates to all those individuals and groups who participate in the purchasing decision-making process, who share some common goals and the risks arising from the decisions. 
D)  A buying centre relates to all those individuals and groups who share some common goals and the risks arising from the decisions.