Most of the world’s supply of uranium currently comes from mines.  It is possible to extract uranium from seawater, but the cost of doing so is greater than the price that uranium fetches on the world market.  Therefore, until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable.

Which of the following would it be most useful to determine in evaluating the argument?

Even though sub-Saharan Africa often evokes images of drought and famine, researchers say that the area is the home of more than 2,000 grains, vegetables, roots, fruits, and other foods that have the possibility for feeding the continent, even other parts of the world.

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas.  In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide.  Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

In her later poems, Phyllis Wheatley’s blending of solar imagery, Judeo-Christian thought and figures, and the images she borrowed from ancient classicism suggesting her range and depth of influences, not the least of which is her African heritage.

Rejecting the apprenticeship model of training social workers in philanthropic agencies, twentieth-century reformer Edith Abbott was convinced of social work education belonging in the university so that students could be offered a broad range of courses dealing with social issues.

Many small roads do not have painted markings along their edges.  Clear edge markings would make it easier for drivers to see upcoming curves and to judge the car’s position on the road, particularly when visibility is poor, and would therefore seem to be a useful contribution to road safety.  However, after Greatwater County painted edge markings on all its narrow, winding roads, the annual accident rate along those roads actually increased slightly.

Which of the following, if true, most helps to explain the increase in accident rate?

Gortland has long been narrowly self-sufficient in both grain and meat. However, as per capita income in Gortland has risen toward the world average, per capita consumption of meat has also risen toward the world average, and it takes several pounds of grain to produce one pound of meat.  Therefore, since per capita income continues to rise, whereas domestic grain production will not increase, Gortland will soon have to import either grain or meat or both.

Which of the following is an assumption on which the argument depends?

For years the beautiful Renaissance buildings in Palitito have been damaged by exhaust from the many tour buses that come to the city.  There has been little parking space, so most buses have idled at the curb during each stop on their tour, and idling produces as much exhaust as driving.  The city has now provided parking that accommodates a third of the tour buses, so damage to Palitito’s buildings from the buses’ exhaust will diminish significantly.

Which of the following, if true, most strongly supports the argument?

Bluegrass musician Bill Monroe, whose repertory, views on musical collaboration, and vocal style were influential on generations of bluegrass artists, was also an inspiration to many musicians, that included Elvis Presley and Jerry Garcia, whose music differed significantly from his own.

Although unhappy with the high rent her company was paying for its suburban office building, the chief executive recognized rental rates for buildings in the suburbs as far lower than it typically is for property that is located within the city limits.

Traces of cultivated emmer wheat have been found among the earliest agricultural remains of many archaeological sites in Europe and Asia.  The only place where the wild form of emmer wheat has been found growing is a relatively narrow strip of southwest Asia.  Since the oldest remains of cultivated emmer wheat yet found are from village sites in the same narrow strip, it is clear that emmer wheat was first domesticated somewhere in that strip.

Which of the following, if true, most strengthens the argument?

The hognose snake puts on an impressive bluff, hissing and rearing back, broadens the flesh behind its head the way a cobra does, feigning repeated strikes, but, having no dangerous fangs and no venom, eventually, if its pursuer is not cowed by the performance, will fall over and play dead.

When Nigeria achieved full independence in 1960, they had already established a federal political structure consisting of three regions based on the three major population clusters that were in its borders.

In the late 1980s, the population of sea otters in the North Pacific began to decline.  There are two plausible explanations for the decline:  predation, possibly by killer whales, or disease. Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.

Which of the following, if true, most seriously weakens the reasoning?