Read this excerpt from A Black Hole Is NOT a Hole. One of the best black-hole clues is X-ray energy. As matter approaches an event horizon, its atoms "shine" with invisible X-rays. Although our eyes can't see the X-rays, we can make detectors that respond to their tremendous energy.

X-ray-catching telescopes make pictures of otherwise invisible X-rays. The pictures reveal that certain areas in outer space are emitting intense X-rays. Each bright location points out where something extraordinary is going on. It is a hint that a black hole might be there.

Why does the author include this description?

to explain why humans cannot see X-rays
to explain how X-rays help scientists study space
to explain that black holes are extraordinary
to explain where black holes are located

Hich line in this excerpt from jonathan swift's "a modest proposal" uses the rhetorical device of irony? and secondly, (there being a round million of creatures in humane figure throughout this kingdom, whose whole subsistence put into a common stock, would leave them in debt two million of pounds sterling), adding those who are beggars by profession, to the bulk of farmers, cottagers and labourers, with their wives and children, who are beggars in effect; i desire those politicians who dislike my overture, and may perhaps be so bold to attempt an answer, that they will first ask the parents of these mortals, whether they would not at this day think it a great happiness to have been sold for food at a year old, in the manner i prescribe, and thereby have avoided such a perpetual scene of misfortunes, as (they have since gone through, by the oppression of landlords, the impossibility of paying rent without money or trade, the want of common sustenance, with neither house nor cloaths to cover them from the inclemencies of the weather,) and the most inevitable prospect of intailing the like, or greater miseries, upon their breed for ever. i profess, in the sincerity of my heart, that( i have not the least personal interest in endeavouring to promote this necessary work, having no other motive than the publick good of my country,) by advancing our trade, providing for infants, relieving the poor, and giving some pleasure to the rich.( i have no children, by which i can propose to get a single penny; the youngest being nine years old, and my wife past child-bearing. reset next)

How did the renaissance represented a break from the medieval period

Read the excerpt from the code book. without much hope of a theoretical breakthrough, cryptanalysts have been forced to look for a technological innovation. if there is no obvious way to reduce the number of steps required for factoring, then cryptanalysts need a technology that will perform these steps more quickly. silicon chips will continue to get faster as the years pass, doubling in speed roughly every eighteen months, but this is not enough to make a real impact on the speed of factoring—cryptanalysts require a technology that is billions of times faster than current computers. consequently, cryptanalysts are looking toward a radically new form of computer, the quantum computer. if scientists could build a quantum computer, it would be able to perform calculations with such enormous speed that it would make a modern supercomputer look like a broken abacus. the author’s purpose in this paragraph is to convince the readers to pursue a career in analysis. explain the need for faster technology in cryptanalysis. entertain with interesting stories about supercomputers. argue for more money to develop a quantum computer.