A study led by scientist Rebecca Kirby at the University of Wisconsin-Madison found that black bears that eat human food before hibernation have increased levels of a rare carbon isotope, ________ due to the higher $^{13}C$ levels in corn and cane sugar. Bears with these elevated levels were also found to have much shorter hibernation periods on average.

Which choice completes the text so that it conforms to the conventions of Standard English? 

The haiku-like poems of Tomas Transtromer, which present nature- and dream-influenced images in crisp, spare language, have earned the Swedish poet praise from leading contemporary ________ them Nigerian American essayist and novelist Teju Cole, who has written that Transtromer's works "contain a luminous simplicity."

Which choice completes the text so that it conforms to the conventions of Standard English? 

Mathematician and meteorologist Edward Lorenz used the metaphor of the "butterfly effect" to explain how seemingly minor events can have major impacts on future weather. According to Lorenz's metaphor, the wind from a butterfly flapping ________ in Brazil might eventually grow into a storm elsewhere across the globe.

Which choice completes the text so that it conforms to the conventions of Standard English? 

Bonnie Buratti of NASA's Jet Propulsion Laboratory ________ data about Saturn's rings collected by the Cassini spacecraft when she made an interesting discovery: the tiny moons embedded between and within Saturn's rings are shaped by the buildup of ring material on the moons' surfaces.

Which choice completes the text so that it conforms to the conventions of Standard English? 

While one requires oxygen and one does ________ and anaerobic respiration are both forms of cellular respiration--that is, they are processes by which cells break down glucose to use as energy.

Which choice completes the text so that it conforms to the conventions of Standard English? 

To serve local families during the Great Depression, innovative New York City librarian Pura Belpre offered storytelling in both English and Spanish, an uncommon ________ celebrated el Dia de los Tres Reyes Magos, an important community holiday; and put on puppet shows dramatizing Puerto Rican folktales.

Which choice completes the text so that it conforms to the conventions of Standard English?

Photosynthesis, the mechanism by which plants use sunlight to turn carbon dioxide and water into ________ is fueled in part by an enzyme called Photosystem II that harvests energy-giving electrons from water molecules.

Which choice completes the text so that it conforms to the conventions of Standard English?

Human-made (synthetic) fibers used in clothes and many other consumer products are more durable than most natural plant ________ the manufacture of synthetic fibers requires toxic chemical solvents that can pollute air and water.

Which choice completes the text so that it conforms to the conventions of Standard English?

After a spate of illnesses as a child, Wilma Rudolph was told she might never walk again. Defying all odds, Rudolph didn't just walk, she ________ the 1960 Summer Olympics in Rome, she won both the 100- and 200-meter dashes and clinched first place for her team in the 4x100-meter relay, becoming the first US woman to win three gold medals in a single Olympics.

Which choice completes the text so that it conforms to the conventions of Standard English?

Rabinal Achi is a precolonial Maya dance drama performed annually in Rabinal, a town in the Guatem highlands. Based on events that occurred when Rabinal was a city-state ruled by a king, _______ had once been an ally of the king but was later captured while leading an invading force against him.

Which choice completes the text so that it conforms to the conventions of Standard English?

During the American Civil War, Thomas Morris Chester braved the front lines as a war correspondent for the _Philadelphia Press_. Amplifying the voices and experiences of Black soldiers ________ of particular importance to Chester, who later became an activist and lawyer during the postwar Reconstruction period.

Which choice completes the text so that it conforms to the conventions of Standard English?

In 1903, environmentalist John Muir guided President Theodore Roosevelt on a scenic, sprawling trip through California's Yosemite Valley. Upon returning from the three-day excursion, Roosevelt ________ to conserve the nation's wilderness areas, a vow he upheld for his remaining six years in office.

Which choice completes the text so that it conforms to the conventions of Standard English?

To survive when water is scarce, embryos inside African turquoise killfish eggs ________ a dormant state known as diapause. In this state, embryonic development is paused for as long as two years--longer than the life span of an adult killfish.

Which choice completes the text so that it conforms to the conventions of Standard English?

In 1637, the price of tulips skyrocketed in Amsterdam, with single bulbs of rare varieties selling for up to the equivalentof $200,000 in today’s US dollars. Some historians ________ that this "tulip mania" was the first historical instance of an asset bubble, which occurs when investors drive prices to highs not supported by actual demand.

Which choice completes the text so that it conforms to the conventions of Standard English?