Because of its accuracy in outlining the Earth's subsurface, the seism

Summary - Author is talking about Seismic-Reflection method and its importance. Then he/she provides details of the method and how it deals with various factors affecting its accuracy.

1. The passage is primarily concerned with

(A) describing an important technique – CORRECT.
(B) discussing a new method – WRONG. Not a ‘New’ method as its not mentioned in the passage that it’s new.
(C) investigating a controversial procedure – WRONG. This option is incorrect for the reason that author is not investigating any controversial procedure.
(D) announcing a significant discovery – WRONG. No author does not say anything about significant discovery.
(E) promoting a novel application – WRONG. No option is given by author.

2. According to the passage, in the seismic-reflection method all of the following have a significant effect on the signal detected by the seismic instruments EXCEPT the

After POE eliminated A, D and E. Got stuck with B and C and eliminated C for the reason that passage mentions ‘each’ n lne-3 “As each source is activated, it generates a wave train that moves… “. Assumed that ‘each’ plays a role in locating every seismic instrument.

(A) presence of unrelated wave trains – WRONG. Mentioned in passage.
(B) placement of the seismic instruments
(C) number of sources in the grid pattern
(D) nature of the reflectivity of the rock interfaces – WRONG. Refer line-4 of passage.
(E) properties of rocks through which the wave train has traveled – WRONG. ‘Rock characteristic’ mentioned in passage.

3. It can be inferred from the passage that the seismic-reflection method would be likely to yield an inaccurate physical profile of the subsurface in which of the following circumstances?

Again using POE eliminated A B and E. Stuck with C and D chose D over C with a reasoning that different sources with similar seismic records would mislead the method to generate similar profile thus inaccuracy.

(A) If the speed at which the wave train moved downward changed – WRONG. Opposite to what we require to infer. Change is necessary for a unique profile
(B) If the receiver were not positioned directly at the wave-train source – WRONG. Not mentioned.
(C) If the rock on one side of a rock interface had similar elastic characteristics to those of the rock on the other side
(D) If the seismic records obtained for the different sources in a grid were highly similar to each other
(E) If there were no petroleum deposits beneath the area defined by the grid of wave-train sources – WRONG. No deposits would also have some unique profile.

4. Which of the following best describes the organization of the passage?

After POE eliminated A B and D. After a brief thought mistook in the thick of moment elements of the method as evidence to mark E the wrong answer as correct.

(A) A method is criticized, and an alternative is suggested. – WRONG. There’s no author’s opinion.
(B) An illustration is examined, and some errors are exposed. – WRONG. Author describes and nowhere examines to expose errors.
(C) An assertion is made, and a procedure is outlined.
(D) A series of examples is presented, and a conclusion is drawn. WRONG. No conclusion is drawn.
(E) A hypothesis is advanced, and supporting evidence is supplied.
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please explain Q2 & Q3.
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1. The passage is primarily concerned with

(A) describing an important technique

The passage describes about a technique and how it is performed to deliver a positive result

(B) discussing a new method

wrong

(C) investigating a controversial procedure

wrong

(D) announcing a significant discovery

wrong

(E) promoting a novel application

Basically as B.


2. According to the passage, in the seismic-reflection method all of the following have a significant effect on the signal detected by the seismic instruments EXCEPT the

(A) presence of unrelated wave trains
(B) placement of the seismic instruments
(C) number of sources in the grid pattern

the seismic-reflection method remains the most important tool in the search for petroleum reserves. In field practice, a subsurface is mapped by arranging a series of wave-train sources, such as small dynamite explosions, in a grid pattern.

The number is not mentioned. C is the correct answer

(D) nature of the reflectivity of the rock interfaces
(E) properties of rocks through which the wave train has traveled


3. It can be inferred from the passage that the seismic-reflection method would be likely to yield an inaccurate physical profile of the subsurface in which of the following circumstances?

(A) If the speed at which the wave train moved downward changed
(B) If the receiver were not positioned directly at the wave-train source
(C) If the rock on one side of a rock interface had similar elastic characteristics to those of the rock on the other side


The seismic records must be processed to correct for positional differences between the source and the receiver, for unrelated wave trains, and for multiple reflections from the rock interfaces.

If all the process described above was similar then would be inaccurate. We do need the differences and then those are adjusted.

[[this line: As rock interfaces are crossed, the elastic characteristics encountered generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments.

If the elastic characteristics are similar on one interface of a rock to the other, then the change in elastic characteristics would be close to zero. if that happens, then net energy would be zero; therefore no energy would be reflected back to the surface, where it is recorded by seismic instruments.]]

(D) If the seismic records obtained for the different sources in a grid were highly similar to each other
(E) If there were no petroleum deposits beneath the area defined by the grid of wave-train sources



4. Which of the following best describes the organization of the passage?

(A) A method is criticized, and an alternative is suggested.
(B) An illustration is examined, and some errors are exposed.
(C) An assertion is made, and a procedure is outlined.

The technique to discover the petroleum is asserted, it is still an important element to find new reservoir and how it is connected is explained.

(D) A series of examples is presented, and a conclusion is drawn.
(E) A hypothesis is advanced, and supporting evidence is supplied.