Seismologists studying the earthquake that struck northern California

Since a colon is used any information after the colon does not have to be a complete sentence. Also, "The unexpected power of the seismic waves" is not a complete sentence

A verb is not present.
The = article
upward = adjective
thrust = noun (subject)
of the seismic waves = prepositional phrase

The colon (:) signals an enumeration of the earthquakes' mysteries. Only A makes a simple and parallel enumeration.

Answer: A

Seismologists studying the earthquake that struck northern California in October 1989 are still investigating some of its mysteries: the unexpected power of the seismic waves, the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.
(A) the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor - Correct
(B) the upward thrust that threw one man straight into the air, and strange electromagnetic signals were detected hours before the temblor - Parallelism issue - strange electromagnetic signal is clause whereas the other two entities are noun phrases
(C) the upward thrust threw one man straight into the air, and hours before the temblor strange electromagnetic signals were detected - Parallelism issue
(D) one man was thrown straight into the air by the upward thrust, and hours before the temblor strange electromagnetic signals were detected - Parallelism issue and distorts the meaning - Seismologists are investigating one man
(E) one man who was thrown straight into the air by the upward thrust, and strange electromagnetic signals that were detected hours before the temblor - distorts the meaning - Seismologists are investigating one man

Answer A

Seismologists studying the earthquake that struck northern California in October 1989 are still investigating some of its mysteries: the unexpected power of the seismic waves, the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.


Seismologists are investigating mysteries, and there are 3 mysteries

1) the unexpected power of the seismic waves
2) the upward thrust that threw one man straight into the air
3) the strange electromagnetic signals detected hours before the temblor

all 3 properties have their own modifiers which give readers more information
Particularly in the 3rd one, "detected" is not a verb. Some people are confused when V+ed is used as a modifier rather than a verb.

Therefore (A) is the correct choice because it also maintains parallelism.

In my view, in this sentence, "the upward thrust that threw one man straight into the air" is an absolute modifier for " the unexpected power of the seismic waves". So, there are actually 2 mysteries:
1.power of the seismic waves
2.strange electromagnetic signals
Am I correct?

(A) the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor
Best option

(B) the upward thrust that threw one man straight into the air, and strange electromagnetic signals were detected hours before the temblor
(1) “strange electromagnetic signals were…” – not parallel with first two items (noun phrases)

(C) the upward thrust threw one man straight into the air, and hours before the temblor strange electromagnetic signals were detected
(1) “the upward thrust threw one man…” – illogical meaning; lack of parallelism with first item in list; (2) logically, the last item in the list (“hours before the...”) isn’t necessarily a “mystery”

(D) one man was thrown straight into the air by the upward thrust, and hours before the temblor strange electromagnetic signals were detected
(1) “one man was thrown straight…” – breaks parallelism with first item in the list

(E) one man who was thrown straight into the air by the upward thrust, and strange electromagnetic signals that were detected hours before the temblor
(1) “one man who was thrown…by the upward thrust…” – illogical meaning; the thrust wouldn’t have literally thrown the man

Solution
There are 3 mysteries – these are to be written in 'phrase form' and not in 'clause form' in order to maintain a parallel structure. Non-underline 1st element ‘the unexpected power of the seismic waves' is NOT a clause. Hence, we need 2 phrase-structure to make a sentence parallel.

Options B, C, D, & E all use 'were' verb i.e. place a clause into parallel structure = Wrong

The correct choice is A

Kudos please if you like the explanation

Seismologists studying the earthquake that struck northern California in October 1989 are still investigating some of its mysteries: the unexpected power of the seismic waves, the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.


(A) the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor- Parallelism is perfect in this option. This is the correct answer.

(B) the upward thrust that threw one man straight into the air, and strange electromagnetic signals were detected hours before the temblor- Parallelism issue

(C) the upward thrust threw one man straight into the air, and hours before the temblor strange electromagnetic signals were detected- Parallelism issue

(D) one man was thrown straight into the air by the upward thrust, and hours before the temblor strange electromagnetic signals were detected- Parallelism issue

(E) one man who was thrown straight into the air by the upward thrust, and strange electromagnetic signals that were detected hours before the temblor- Parallelism issue

Dear Friends,

Here is a detailed explanation to this question-

Meaning is crucial to solving this problem:
Understanding the intended meaning is key to solving this question; the intended meaning of the crucial part of this sentence is that some of the mysteries of the earthquake are the unexpected power of the seismic waves, the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.

Concepts tested here: Meaning + Parallelism + Awkwardness/Redundancy

• All elements in a list must be parallel.

A: Correct.
1/ This answer choice uses the phrase "the upward thrust that threw one man", conveying the intended meaning - that the upward thrust was one of the mysteries of the earthquake.
2/ Option A maintains parallelism among "the unexpected power of the seismic waves", "the upward thrust that threw one man straight into the air", and "the strange electromagnetic signals detected hours before the temblor".
3/ Option A is free of any awkwardness or redundancy.

B:
1/ This answer choice fails to maintain parallelism among "the unexpected power of the seismic waves", "the upward thrust threw one man straight into the air", and "hours before the temblor strange electromagnetic signals were detected"; remember, all elements in a list must be parallel.

C:
1/ This answer choice fails to maintain parallelism among "the unexpected power of the seismic waves", "the upward thrust that threw one man straight into the air", and "strange electromagnetic signals were detected hours before the temblor"; remember, all elements in a list must be parallel.

D:
1/ This answer choice fails to maintain parallelism among "the unexpected power of the seismic waves", "one man was thrown straight into the air by the upward thrust", and "hours before the temblor strange electromagnetic signals were detected"; remember, all elements in a list must be parallel.
2/ Option D uses the passive construction "one man was thrown", leading to awkwardness and redundancy.

E:
1/ This answer choice alters the meaning of the sentence through the phrase "one man who was thrown straight into the air by the upward thrust"; the construction of this phrase incorrectly implies that the man was one of the mysteries of the earthquake; the intended meaning is that the upward thrust was one of the mysteries of the earthquake.

Hence, A is the best answer choice.

All the best!
Experts' Global Team

I picked A but I was a bit unsure about the use of "that" in A, what is it referring to?