Researchers at Cornell University have demonstrated that homing pigeon

A and C do not have verb ,D and E passive ,B is our choice.

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Ok the question is providing facts, therefore everything will be in Simple Present or Simple Past tense, depending on the context. Now here everything(non-underlined) is in Simple Present tense.
Moving on there are number of facts of listed and each of them is in Active Voice, so we see for Active Voice.
And last but not the least Parallelism!! Every facts listed should be Parallel to each other

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Researchers at Cornell University have demonstrated that homing pigeons can sense changes in the earth's magnetic field, see light waves that people cannot see, detect low-frequency sounds from miles away, sense changes in air pressure, and can identify familiar odors.

(A) sense changes in air pressure, and can identify familiar odors ---> Parallelism is not maintained e.g: It is right to write:
I can drive Cars, wash Bikes, and break biscuits
OR
I can drive Cars, can wash Bikes, and can break biscuits, but it will be wrong to write I can drive Cars, wash Bikes, and can break biscuits.

(B) can sense changes in air pressure, and can identify familiar odors ---> Same error as A

(C) sense changes in air pressure, and identify familiar odors ---> Correct!

(D) air pressure changes can be sensed, and familiar odors identified ---> Passive Voice and very awkward construction

(E) air pressure changes are sensed, and familiar odors identified -------> Very Very awkward construction I mean just read the sentence Pigeons can air pressure changes are sensed

Parallelism of : sense...., see...., detect...., sense...., and identify...

Answer: C

Researchers at Cornell University have demonstrated that homing pigeons can sense changes in the earth's magnetic field, see light waves that people cannot see, detect low-frequency sounds from miles away, sense changes in air pressure, and can identify familiar odors.

The structure is Pigeons can do X , Y ,Z , M and N ( The Can in the last part in A is redundant )



Only C has this structure - hence C

Official Explanation :

This question requires you to choose an answer that completes a series of parallel verbs.
Choice A is incorrect because the can before identify breaks a parallel sequence of verbs that complete the can in line 2: A states, homing pigeons can sense, . . see, . . . detect,, . sense, . .' and can identify.

Choice B makes the problem worse by adding can before two verbs so that both are nonparallel.

Choice C is best.

Choices D and E wrongly substitute independent clauses for the verb phrases in C that continue the parallel construction.

Researchers at Cornell University have demonstrated that homing pigeons can sense

changes in the earth's magnetic field,
see light waves that people cannot see,
detect low-frequency sounds from miles away,

sense

changes in air pressure, and
identify familiar odors.

IMHO (C) as well for parallelism issue...

Researchers at Cornell University have demonstrated that homing pigeons can sense changes in the earth's magnetic field, see light waves that people cannot see, detect low-frequency sounds from miles away, sense changes in air pressure, and can identify familiar odors.

(A) sense changes in air pressure, and can identify familiar odors - Parallelism issue- can is already is a part of the stem and thus "can identify familiar odors' makes it incorrect

(B) can sense changes in air pressure, and can identify familiar odors - Parallelism issue - here we two can in the inner parallel elements

(C) sense changes in air pressure, and identify familiar odors - Correct

(D) air pressure changes can be sensed, and familiar odors identified - Parallelism issue - verb phrase is not parallel to independent clauses

(E) air pressure changes are sensed, and familiar odors identified - Parallelism issue - verb phrase is not parallel to independent clauses

Answer C

This is fundamentally a parallelism issue.

The part of the sentence that carries over to the rest of each element in the list is "Researchers at Cornell...can". Seek to determine whether that part of the sentence makes sense when placed in front of each of the items in the list.

Only C does not violate the issues of parallelism.

This problem is related to parallelism with lists, so we can eliminate the answer choices that are not in the list order.
So, D and E are the first to eliminate.
Now in A, B, and C.
A has an extra 'can' in the second half, so eliminate A.
B has an extra 'can' on both sides, so eliminate B also.
That leaves us with option C, The correct option.

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