GMAT Exam Preparation Material | Graduate Management Admission Test (2021)

Doctor: People who have grown up on farms and have been frequently exposed to germs from farm animals are much less likely to develop allergies than are people who were raised in more sanitary environments. This suggests that childhood exposure to certain microorganisms improves the function of the immune system.
In order to assess the strength of the doctor's argument, it would be most helpful to know which of the following?

Soil salinization―the process by which soil acquires excess soluble salt, adversely affecting pasture or crop growth―is regarded as Australia's most serious environmental problem. Cope, whose 1958 investigation is considered the earliest survey of salt-affected areas in Victoria, hypothesized that surplus rainwater mobilized soluble salt stored in the permeable layer of soil, causing it to accumulate above an impermeable layer and then discharge downslope or onto a valley floor. In the late 1970s, however, Jenkin identified saline water underground as the main and immediate (though not ultimate) source of the salt, and hypothesized that the spread of salinity resulted from a rise in that groundwater. He attributed the rise to a decrease in coverage by water-absorbing trees and other vegetation at some ill-defined point in Australia's post-settlement history.
However, more-recent research suggests there was no rise in post-settlement groundwater levels. Furthermore, soil salinity probably antedated European settlement: early cartographic evidence indicates that some streams were saline when Europeans arrived. Dahlhaus suggests that salt accumulation resulted from marine incursions several million years ago, when parts of Victoria may have been submerged―as well as from transport of salt from the sea by wind and rain. Dahlhaus also notes that various minerals dissolved in groundwater by weathering may have produced salt.
The passage is primarily concerned with discussing

Legislator: Relatively few people in this society object to allowing the potential use of gene replacement techniques to treat disease, but most react negatively to allowing the use of such techniques to enhance people's performance in competitive sports. A clear distinction should therefore be made between medical treatment and performance enhancement when regulations concerning gene replacement are being formulated, because otherwise__________,
Which of the following most logically completes the passage?

Soil salinization―the process by which soil acquires excess soluble salt, adversely affecting pasture or crop growth―is regarded as Australia's most serious environmental problem. Cope, whose 1958 investigation is considered the earliest survey of salt-affected areas in Victoria, hypothesized that surplus rainwater mobilized soluble salt stored in the permeable layer of soil, causing it to accumulate above an impermeable layer and then discharge downslope or onto a valley floor. In the late 1970s, however, Jenkin identified saline water underground as the main and immediate (though not ultimate) source of the salt, and hypothesized that the spread of salinity resulted from a rise in that groundwater. He attributed the rise to a decrease in coverage by water-absorbing trees and other vegetation at some ill-defined point in Australia's post-settlement history.
However, more-recent research suggests there was no rise in post-settlement groundwater levels. Furthermore, soil salinity probably antedated European settlement: early cartographic evidence indicates that some streams were saline when Europeans arrived. Dahlhaus suggests that salt accumulation resulted from marine incursions several million years ago, when parts of Victoria may have been submerged―as well as from transport of salt from the sea by wind and rain. Dahlhaus also notes that various minerals dissolved in groundwater by weathering may have produced salt.
The passage most strongly suggests that the author agrees with which of the following?

Daniel: Historically, railroads substantially altered the course of the United States economy, enabling the country to enjoy unprecedented growth in the nineteenth century.
Robert: It's true that growth required cheap inland transportation, which railroads provided. But with government support similar to the massive land grants that subsidized rapid railroad expansion, canals and roads could have had the same effect.
Which of the following is most likely a point that Robert believes is at issue between Daniel and himself?