1. By 1784, Wolfgang Amadeus Mozart was internationally renowned as the composer of The Marriage of Figaro, and consequently received a commission from the Prague Opera House to compose another opera.

The resulting product was Don Giovanni, which tells the tale of a criminal and seducer who nevertheless evokes sympathy from audiences, and whose behavior fluctuates from moral crisis to hilarious escapade.

While Don Giovanni is widely considered to be Mozart’s greatest achievement, eighteenth century audiences in Vienna — Mozart’s own city — were ambivalent at best. The opera mixed traditions of moralism with those of comedy — a practice heretofore unknown among the composer’s works — creating a production that was not well liked by conservative Viennese audiences. Meanwhile, however, Don Giovanni was performed to much acclaim throughout Europe.

Ques 2. The primary purpose of the passage is to

2. Follow the money and you will end up in space. That’s the message from a first-of-its-kind forum on mining beyond Earth. Convened in Sydney by the Australian Centre for Space Engineering Research, the event brought together mining companies, robotics experts, lunar scientists, and government agencies that are all working to make space mining a reality. The forum comes hot on the heels of the 2012 unveiling of two private asteroid-mining firms. Planetary Resources of Washington says it will launch its first prospecting telescopes in two years, while Deep Space Industries of Virginia hopes to be harvesting metals from asteroids by 2020. Another commercial venture that sprung up in 2012, Golden Spike of Colorado, will be offering trips to the moon, including to potential lunar miners.

The author of Passage mentions several companies primarily to

3. Stars create energy through the process of fusion. When a star explodes—a phenomenon called a supernova—so much energy is released that heavy metals such as iron and gold are formed, seeding surrounding hydrogen clouds. Newer stars therefore contain more heavy elements in their atmospheres. Heavy elements form the materials that make up our planet (and even human bodies). It is believed that for a system of planets such as our solar system to form around a star during cloud contraction, the presence of these heavy elements in the cloud is a necessity.

A molecular cloud can become unstable and collapse by the force of gravity, overcoming outward thermal pressure of the constituent gases. At a given temperature and density, two critical measures of size, Jeans mass and Jeans length, can be calculated. If the size of the cloud exceeds either of these critical values, gravity will ultimately win, and the probability of eventual cloud contraction is high. However, some outside influence is still evidently required for a theoretically unstable cloud to initiate collapse.

The natural rotation of a galaxy can slowly alter the structure of a cloud, for instance. Surrounding supernovae can generate shock-waves powerful enough to affect the debris in other clouds, forcing the debris inward and possibly causing contraction to begin. One theory states that density waves propagating through spiral structures can also sufficiently stimulate clouds to cause contraction.

 Which of the following inferences about our solar system is best supported by the passage?

4. By 1784, Wolfgang Amadeus Mozart was internationally renowned as the composer of The Marriage of Figaro, and consequently received a commission from the Prague Opera House to compose another opera.

The resulting product was Don Giovanni, which tells the tale of a criminal and seducer who nevertheless evokes sympathy from audiences, and whose behavior fluctuates from moral crisis to hilarious escapade.

While Don Giovanni is widely considered to be Mozart’s greatest achievement, eighteenth century audiences in Vienna — Mozart’s own city — were ambivalent at best. The opera mixed traditions of moralism with those of comedy — a practice heretofore unknown among the composer’s works — creating a production that was not well liked by conservative Viennese audiences. Meanwhile, however, Don Giovanni was performed to much acclaim throughout Europe.

The primary purpose of the passage is to

5. Every day, millions of shoppers hit the stores in full force—both online and on foot—searching frantically for the perfect gift. Last year, Americans spent over $30 billion at retail stores in the month of December alone. Aside from purchasing holiday gifts, most people regularly buy presents for other occasions throughout the year, including weddings, birthdays, anniversaries, graduations, and baby showers. This frequent experience of gift-giving can engender ambivalent feelings in gift-givers.

The authors most likely use the examples in the passage to highlight the

6. The chemical formula of deoxyribonucleic acid (DNA) is now well established. The molecule is a very long chain, the backbone of which consists of a regular alternation of sugar and phosphate groups. To each sugar is attached a nitrogenous base, which can be of four different types. Two of the possible bases—adenine and guanine—are purines, and the other two—thymine and cytosine—are pyrimidines. So far as is known, the sequence of bases along the chain is irregular. The monomer unit, consisting of phosphate, sugar and base, is known as a nucleotide. The first feature of our structure which is of biological interest is that it consists not of one chain, but of two. These two chains are both coiled around a common fiber axis. It has often been assumed that since there was only one chain in the chemical formula there would only be one in the structural unit. However, the density, taken with the X-ray evidence, suggests very strongly that there are two.

In the paragraph , what do the authors claim to be a feature of biological interest?