MISSING LETTERS 20

Zebrafish are tiny, striped fish native to South Asia that are clos___ related to minnows. They m____ seem to share few characteristics w___ humans, but, in fact, zebrafish and peo___ share ab___ 70 percent of their genes. The little finned creatures al__ have a lot of the same body parts found in a human being. Bec____ of this similarity, zebrafish a__ replacing mice as the mo__ preferred animal species for medical experimentation.

Titan is the largest moon orbiting Saturn. Until January 14, 2005, wh__ a NASA-designed probe called Huygens landed o_ its surface, scientists knew little ab___ Titan d__ to its distance fr__ Earth and a thick, clou__ atmosphere th__ obscured its geological characteristics. Fly-by missions are of little use in studying Titan; the be__ way to explore the moon is to send a spacecraft plunging tow___ its surface. The Huygens mission was an enormously successful first step toward unraveling Titan's mysteries.

In the end, Huygens landed gently o_ a soft substance, sending back 100 remarkable images of beach-like terrain. Titan, it turns o__, is the on__ known body in the solar system containing liquid. Altho___ there is no water, liquid hydrocarbons apparently flow thro___ rivers carved in__ Titan's surface. Huygens did not directly spot a__ of this liquid, but it snapped photos of winding riverbeds. Titan's surface shows signs of flooding, as well as methane rain erosion. Unfortunately, Huygens w__ only able to explore Titan for 72 minutes bef___ its batteries expired

Most of the structures at the Acropolis w___ decimated by the Persians in 480 BC, but Athenian ruler Pericles reconstructed the citadel ab___ three decades later du____ Athens' Golden Age. Af___ a series of military victories, so__ 200 cities in the Aegean region paid Athens enormous sums to protect them, a__ that wealth funded the massive construction effort. It was during this period that the Parthenon, the crown jewel of the Acropolis, w__ built. The temple was half the size of a football field, and it was surrounded by 46 towering marble columns.

The nobility of Renaissance ltaly entertained impor____ visitors with music, mime, a__ dance. These court shows, called spectacles, w___ magnificent celebrations that of___ included hundreds of performers. Florentine noblewoman Catherine de' Medici brought court dancing with her to France wh__ she married King Henry ll. Dur___ this period, Catherine commissioned a spectacle f__ the celebration of the marriage of the Duke of Joyeuse to Marguerite of Lorraine. This is looked up__ as the birth of ballet.

Lakes are large bodies of water surrounded by land. They c__ be found in a wide variety of sizes, shapes, and depths, a__ they can contain fresh as well as salt water. lt is possible to classify them by the way they w___ formed. Tectonic lakes, f__ instance, are created wh__ movements of the plates that form the earth's crust create rifts o_ depressions in the ground that are subsequently filled with water. Tectonic lakes are usu____ steep in slope. They tend to be formed in groups, and they are generally ve__ deep compared to other lakes

The on__ purpose of fine art is to give aesthetic pleasure. Consider the Mona Lisa, Leonardo da Vinci's mo__ famous painting. It serves no utilitarian func____. One cannot do anything w___ it except appreciate its beauty, lifelike accuracy, a__ masterful brushwork. Now think of a coffee mug bearing the image of the Mona Lisa, the kind one m____ find in a museum gift shop.

Placental mammals a__ distinguished by the fact th__ they have a well-developed placenta, wh___ is an organ in the mother's womb that provides nourishment t_ a developing fetus. Because placent___ provide m___ nourishment to their young in the womb, they have lar__ babies that are well developed a__ less dependent on their mothers th__ their marsupial counterparts.

Although marsupials al__ have a placenta, their offspring develop out____ their bodies in a pouch. The marsupial placenta provides nutrition in the earliest stages of the pregnancy, a__ the fetus is on__ attached to it for a v___ brief period of time. Wh__ they are born, marsupial babies are blind w___ no ears or back legs, features that emerge whi__ they are in the mother's pouch.

The law of demand states that there is an inverse relationship bet____ the price of goods and the quantity that consumers buy. In o____ words, if the price of goods is high, fewer goods w___ be sold. And, correspondingly, it is wh__ prices are at their lowest that goods virtually fly o__ the shelves. This is, of course, w__ stores put products on sale. They are willing to sacrifice so__ revenue from each individual item beca___ their total revenue will be greater based on the increased number of items they sell. However, Veblen goods and Giffen goods a__ an exception to this rule.