Macrophages are cells that play a role in there sponse of the immune system of mice and other mammals to invasive organisms such as bacteria. Unlike other mice, mice that are genetically incapable of making these particular cells do not show elevated levels of nitrates when infected with bacteria.

The statements above, if true, provide the most support for which of the following conclusions?

By competing with rodents for seeds, black ants help control rodent populations that pose a public health risk. However, a very aggressive species of blank ant, the Loma ant, which has recently invaded a certain region, has a venomous sting that is often fatal to humans. Therefore, the planned introduction into that region of ant flies, which prey on Loma ants, would benefit public health.

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

Which of the following, if true, most logically completes the argument?

Aroca County's public schools are supported primarily by taxes on property. The county plans to eliminate the property tax and support schools with a new three percent sales tax on all retail items sold in the county. Three percent of current retail sales is less than the amount collected through property taxes, but implementation of the plan would not necessarily reduce the amount of money going to Aroca County public schools, because ______.

Business Analyst: National Motors began selling the Luxora-its new model of sedan—in June. Last week, National released sales figures for the summer months of June, July, and August that showed that by the end of August only 80,000 Luxoras had been sold. Therefore, National will probably not meet its target of selling 500,000 Luxoras in the model's first twelve months.

Which of the following would be most useful to establish in order to evaluate the analyst's prediction?

Which of the following most logically completes the argument?

A significant number of Qualitex Corporation's department heads are due to retire this year. The number of employees other than current department heads who could take on the position of department head is equal to only about half of the expected vacancies. Oualitex is not going to hire department heads from outside the company or have current department heads take over more than one department, so some departments will be without department heads next year unless Qualitex ______.

Vorland's government is planning a nationwide ban on smoking in restaurants. The objection that the ban would reduce restaurants' revenues is ill founded. Several towns in Vorland enacted restaurant smoking restrictions five years ago. Since then, the amount the government collects in restaurant meal taxes in those towns has increased 34 percent, on average, but only 26 percent elsewhere in Vorland. The amount collected in restaurant meal taxes closely reflects restaurants' revenues.

Which of the following, if true, most undermines the defense of the government's plan?

Shipping Clerk: The five specially ordered shipments sent out last week were sent out on Thursday. Last week, all of the shipments that were sent out on Friday consisted entirely of building supplies, and the shipping department then closed for the weekend. Four shipments were sent to Truax Construction last week, only three of which consisted of building supplies.

If the shipping clerk's statements are true, which of the following must also be true?

Editorial: In Ledland, unemployed adults receive government assistance. To reduce unemployment, the government proposes to supplement the income of those who accept jobs that pay less than government assistance, thus enabling employers to hire workers cheaply. However, the supplement will not raise any worker's income above what government assistance would provide if he or she were not gainfully employed. Therefore, unemployed people will have no financial incentive to accept jobs that would entitle them to the supplement.

Which of the following, if true about Ledland, most seriously weakens the argument of the editorial?

In Rubaria, excellent health care is available to virtually the entire population, whereas very few people in Terland receive adequate medical care. Yet, although the death rate for most diseases is higher in Terland than in Rubaria, the percentage of the male population that dies from prostate cancer is significantly higher in Rubaria than in Terland.

Which of the following, if true, most helps to explain the disparity between the prostate cancer death rate in Rubaria and Terland?

In Brindon County, virtually all of the fasteners-such as nuts, bolts, and screws-used by workshops and manufacturing firms have for several years been supplied by the Brindon Bolt Barn, a specialist wholesaler. In recent months many of Brindon County's workshops and manufacturing firms have closed down, and no new ones have opened. Therefore, the Brindon Bolt Barn will undoubtedly show a sharp decline in sales volume and revenue for this year as compared to last year.

The argument depends on assuming which of the following?