Some friends are trying to make wine in their basement. they've added yeast to a sweet grape juice mixture and have allowed the yeast to grow. after several days they find that sugar levels in the grape juice have dropped, but there's no alcohol in the mixture. the most likely explanation is that
(a) the mixture needs less oxygen; yeast only produce alcohol in the absence of oxygen
(b) the mixture needs more sugar; yeast need a lot of energy before they can begin to produce alcohol
(c). the mixture needs more oxygen; yeast need oxygen to break down sugar to produce alcohol
(d)the mixture needs less sugar; high sugar concentrations stimulate cellular respiration, and alcohol is not a by-product of cellular respiration