To make red wine, fermentation occurs with the pulp and skins together

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!

Official Explanation:

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.

A. yeast is converting the sugars into ethanol as carbon dioxide evaporates
B. yeast converts the sugars into ethanol as carbon dioxide was evaporated
C. yeast have converted the sugars into ethanol with an evaporating of carbon dioxide
D. carbon dioxide is evaporating, with the converting of sugars into ethanol by yeast
E. carbon dioxide has evaporated, with the yeast converting the sugars into ethanol

A review of our answer choices shows that verb tense is the deciding factor in this sentence, and we also have a split in the word joining the two clauses (as or with). When verb tense is important, it is essential to look at the portion of the sentence that is not underlined. This will give us clues about what tenses we need to match to remain parallel and grammatical.

In the first independent clause, we have a simple present tense verb (occurs). In the dependent clause connected to the underline portion, we have a present progressive tense verb (are sitting) and the subordinate conjunction “while.” “While” tells us the underlined portion of the sentence is happening at the same time. Any verbs in the underlined portion should be in the present tense; nothing should be in the past tense. Option B uses “was evaporated,” which is the past tense and passive. It cannot be the correct answer.

To further narrow our choices, let’s look at the as/with situation. “As” clearly expresses a simultaneous sequence of events—yeast converting the sugars is happening at the same time as the carbon dioxide evaporates. “With” could mean that one event must lead to another or it could mean they are happening at the same time. “With” makes the sentence ambiguous while “as” does not. Additionally, the options that use “with” have to use a gerund (-ing verb form acting as a noun), which can be awkward (the converting of, an evaporating of). Given these two reasons, “with” is not the best choice. Options C, D, and E cannot be the best answers.

This leaves us with Option A. It uses the present progressive and simple present and clearly shows the simultaneous nature of these actions.

Option A is the best answer.

Well done, sampriya! You cracked the code! Great job focusing on a combination of verb tenses, meaning, and active/passive voice!

Kudos to you!

Well done, Raxit85! Great job catching the changes in meaning and verb issues! While option A still might sound "off" to you, you were smart to leave it be and look to other options for errors, rather than just saying "it's wrong because it sounds weird." Even the correct options on the GMAT sometimes don't sound the way we would write them!

Kudos to you!

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!

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.

Quick read-through reveals that we deal with parallelism and meaning. Somethings is happening while grapes are sitting. So, the underlined part must be parallel to "grapes are sitting".

A. yeast is converting the sugars into ethanol as carbon dioxide evaporates
B. yeast converts the sugars into ethanol as carbon dioxide was evaporated
C. yeast have converted the sugars into ethanol with an evaporating of carbon dioxide
D. carbon dioxide is evaporating, with the converting of sugars into ethanol by yeast
This option is parallel technically, but meaning has no sense. Also, the part in blue is nonsensical.
E. carbon dioxide has evaporated, with the yeast converting the sugars into ethanol

Only option (A) maintains proper meaning and parallelism.

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.