NASA recently published a report cautioning that many of the

The answer would be D and this case in point of jumbled explanations in practice tests + low quality answers
Both the choices are dismal - but given these are the only 2 option

D: much of the debris that is in space and satellites and spacefaring vessels are exposed to poses
This above though long sentence correctly links the subject, to the verb to the modifier...

E: much of the space debris to which satellites and spacefaring vessels are exposed poses

are exposed is wrong idiom - exposed needs a "to" - exposed to, exposed from, etc

between D and E --- "and" vs "to which" both will work and yes "to which" might be better. But in absence of correct idiom - D would be correct grammatically.

Much should be used over Many because space debris is not countable
"debris that is in space" is too wordy

Hence, E
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There are two major problems with the original sentence: (split is much - many / pose - poses)
1. Much vs many : Debries = uncountable = much (such as so much money vs so many dollars where money is uncountable and dollars is countable )
2.Subject verb agreement: pose vs poses Much debris is a singular subject and fits with poses.

NASA recently published a report cautioning that many of the space debris to which satellites and spacefaring vessels are exposed pose a significant risk of damaging or destroying satellites and vessels in instances of accidental impact.

A: many of the space debris to which satellites and spacefaring vessels are exposed pose - out due to error 1
B: many of the space debris that satellites and spacefaring vessels are exposed to poses - out due to error 1 & 2 many - plural => pose
C: many of the debris that is in space and that satellites and spacefaring vessels are exposed to pose - out due to error 1
D: much of the debris that is in space and satellites and spacefaring vessels are exposed to poses -wordy construction. No need to classify derbies
E: much of the space debris to which satellites and spacefaring vessels are exposed poses - correct option.
Answer - E

Exposed to pose/poses is incorrect usage,hence eliminate b,c,d.Between a and e,E because of correct tense and the usage of poses.

Its against Much of the debris vs many of the debris---
as we cannot count debris it should be much of the debris
as much of debris is singular the verb should be poses

we are left with D and E. D is wrong as satellites and spacefaring vessels are exposed to this is modifying nothing

E is perfect

core sentence:
debris poses risk
debris is non-countable , so we use "much". Eliminate A,B and C
D distort the meaning by saying the debris, the satellite and the vessels are exposed
E- correct

E for me.

much of the space debris is correct. Also "much of the space debris" is singular.

Use of 'many' rules out A, B and C.
D is awkward
E is the right Ans

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Answer must be (D) for the highlighted errors in the given options.
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NASA recently published a report cautioning that many of the space debris to which satellites and spacefaring vessels are exposed pose a significant risk of damaging or destroying satellites and vessels in instances of accidental impact.

A: many of the space debris to which satellites and spacefaring vessels are exposed pose -> space debris is uncountable, so "many" is incorrect to use. Incorrect.
B: many of the space debris that satellites and spacefaring vessels are exposed to poses -> Same as A. Incorrect.
C: many of the debris that is in space and that satellites and spacefaring vessels are exposed to pose -> Same as A. Incorrect.
D: much of the debris that is in space and satellites and spacefaring vessels are exposed to poses -> " debris that is in space" can be said as "space debris". Incorrect.
E: much of the space debris to which satellites and spacefaring vessels are exposed poses -> It is better. Let's keep it.

So, I think E.