What Is the Major Obligation for Being a Member of 'Biosphere

What is the major obligation for being a member of 'Biosphere hosts' association in the hospitality industry?

A) Within two years of certification, the restaurant needs to source 50% of its food products from outside of the biosphere area
B) More than 50% of its beverages and the ingredients of more than six dishes need to be sourced from within of the state of Baden Württemberg
C) The restaurants and adjacent hotels need to become EMAS-certified
D) All of answers are correct