snoep wrote:
To make red wine, fermentation occurs with the pulp and skins together, and while the crushed grapes are sitting, yeast is converting the sugars into ethanol as carbon dioxide evaporates.
While indicates there are multiple actions happening at the same time. That gives us the good view to proceed with POE.
A. yeast is converting the sugars into ethanol as carbon dioxide evaporates
while grapes are sitting , yeast is converting sugars -> looks ok, do i need yeast as a subject doing the conversion? Would not solely reject the AC if i don't like it. If i don't find any better choice, i would choose this, hence keep this answer.
B. yeast converts the sugars into ethanol as carbon dioxide was evaporated
While requires simultaneous actions so 'was evaporated' puts the action in the past and does not fit intended parallel actions.
C. yeast have converted the sugars into ethanol with an evaporating of carbon dioxide
While grapes are sitting , yeast have converted... Again this suggests conversion started before action of grapes sitting , not the simultaneous action. And we don't know what is 'with' modifying here - yeast, or conversion, sugars or ethanol. Its not clear.
D. carbon dioxide is evaporating, with the converting of sugars into ethanol by yeast
while grapes are sitting , carbon dioxide is evaporating. Ok, we have one simultaneous action. the actual process of conversion is a part of With modifier so it doesn't indicate the ongoing parallel action. Also, what is 'With' modifying. Is the carbon dioxide with the converting of sugars into ethanol is evaporating or process of evaporation is with the converting of sugar. Meaning of the sentence is very unclear.
E. carbon dioxide has evaporated, with the yeast converting the sugars into ethanol
has evaporated suggests evaporation happened in the past, as wrong in some of the above choices, sequencing of the actions is not required. Carbon dioxide has evaporated has become the main aspect in the sentence. Whereas the process of conversion as carbon dioxide evaporates is the highlight of the intended meaning. Just as other options, this option also incorrectly uses with modifier.
A is best among the options!
Another great explanation,
snoep! This was a tricky one because the correct choice may still sound "off" to you, but it is the only one that conveys the intended meaning clearly. We may not choose to write the sentence that way in our own writing, but that's the fun of the GMAT - sometimes even the correct answers might sound odd.
Kudos to you!