Geologists believe that the warning signs for a major earthquake may include sudden fluctuations in local seismic activity, tilting and other deformations of the Earth's crust, changing the measured strain across a fault zone, and varying the electrical properties of underground rocks.
(A) changing the measured strain across a fault zone, and varying
(B) changing measurements of the strain across a fault zone, and varying
(C) changing the strain as measured across a fault zone, and variations of
(D) changes in the measured strain across a fault zone, and variations in
(E) changes in measurements of the strain across a fault zone, and variations among
This question is based on Parallelism.
The sentence lists the warning signs for a major earthquake – sudden fluctuations in local seismic activity, tilting and other deformations of the earth’s crust,…….
Since the second item in the list begins with a gerund (‘ing’ form of the verb acting as a noun), we may be misled into using the ‘ing’ form for the other items in the list. However, the list contains noun phrases and that’s the structure to be maintained for the other two items in the list.
In Option A, ‘changing’ and ‘varying’ act as participles. To make them parallel to the other items in the list, they should have been phrased as such – changing of the measured strain and varying of the electrical properties. However, the sentence would become wordy and awkward and distort the meaning. So, Option A can be eliminated.
Option B contains a noun at the beginning and is therefore slightly more parallel in structure. However, this option changes the meaning even more by changing “measured strain” to "measurements of the strain”. This phrasing implies that the measurements are changing, and not the strain itself as is the intended meaning. So, Option B can be eliminated.
Option C also lacks parallelism. It retains the participle ‘changing’, though ‘varying’ has been more appropriately changed to ‘variations’. So, Option C can also be eliminated.
Option E distorts the meaning of the sentence. The meaning implied by this option is that it is the measurements that are changed, not the strain.
This option also replaces the preposition ‘in’ with ‘among’, a change that is unnecessary.
This option contains the noun forms - ‘changes’ and ‘variations’ – that are parallel to 'fluctuations' and 'deformations'. Therefore, D is the most appropriate option.