Sentence correction question - The Bentley trench

[Xenophontis]

Hello.
I have a question regarding problem 10 on page 203 of the Sentence Correction guide, 5th edition.
The correct answer to this question is "The Bentley trench, situated at more than a mile and a half below sea level and completely covered by Antarctic glaciers, IS the lowest point on the planet not under the oceans."

I understand the wrong usage of "and", but the way I would solve the problem is that, in addition to changing "and it is" to "is" I would also remove the comma, since the second part of the sentence provides essential information.

Why is there a comma, although we have an essential modifier?

Thank you.

[jnelson0612]

Hello.
I have a question regarding problem 10 on page 203 of the Sentence Correction guide, 5th edition.
The correct answer to this question is "The Bentley trench, situated at more than a mile and a half below sea level and completely covered by Antarctic glaciers, IS the lowest point on the planet not under the oceans."

I understand the wrong usage of "and", but the way I would solve the problem is that, in addition to changing "and it is" to "is" I would also remove the comma, since the second part of the sentence provides essential information.

Why is there a comma, although we have an essential modifier?

Thank you.

Quick question--which comma would you remove? Thanks!

[Xenophontis]

it's the comma between the words "glaciers" and "is" : "covered by Antarctic glaciers, IS the lowest point"

I'd remove the comma that's situated before "is", since the following sentence tells us something new.

[tim]

What do you mean by "the following sentence"? The issue here is that "The Bentley trench is the lowest point on the planet not under the oceans." If you want to include a modifying phrase that has a comma on one end, it has to have a comma at the other end as well. Although the comparison is not exact, think of the first comma as an open parenthesis and the second one as a close parenthesis. You can't have one without the other.