Which of the following statements, if true, most weakens the authors' suggestion that the record of X-ray binaries provides evidence for the existence of black holes?

Utility Corp, a company with a specific level of cash in its budget, has been clearing uninhabited land near a national park for the construction of a coal plant. This practice continues even though greater annual profits can be made from a nuclear plant, which will not damage the nearby park, than from a coal plant, which will injure the habitat.

Which of the following, if true, most helps to explain why Utility Corp has been pursuing the less profitable of the two economic activities mentioned above?

The author is primarily concerned with

An online retailer that makes its deliveries through a private shipping company has determined that, unlike before, now it can profitably begin making deliveries seven days a week, not just six days a week. Delivering a given number of shipments within a narrower window of time tends to be more cost effective, because, on average, delivery trucks will be able to exploit economies in their driving routes and will incur lower average shipping costs per dollar of delivered goods per hour. Nevertheless, the retailer expects profits to rise with the change.

Which of the following, if true, provides the best reason for the expectation?

Nanotechnology may pose risks in the coming decades as we find it increasingly commonplace to introduce small robots into our bodies. But the fact that these robots might be invisible to the naked eye doesn't mean we are helpless against them. After all, since the initial development of germ theory, we have designed and continuously improved upon ways to protect ourselves from a variety of germs.

In the passage, the author develops the argument by