Based on genetic evidence, archaeologists have generally agreed that reindeer domestication began in the eleventh century CE. However, since uncovering fragments of a 2,000-year-old reindeer training harness in northern Siberia, ______blank may have begun much earlier.

The Mission 66 initiative, which was approved by Congress in 1956, represented a major investment in the infrastructure of overburdened national ______blank it prioritized physical improvements to the parks’ roads, utilities, employee housing, and visitor facilities while also establishing educational programming for the public.

On April 5, 1977, Kitty Cone and 150 other disability rights activists entered a San Francisco federal building. After pleading for years—to no effect—for the passage of key antidiscrimination legislation, ______blank until their demands were addressed. Finally, on April 28, the legislation was signed.

Ten of William Shakespeare’s plays are classified as histories. Although each one of these plays, which include Henry V and Richard III, ______blank on a single historical figure (specifically, an English king), some, such as Henry VI Part One and Henry VI Part Two, feature different episodes from the same monarch’s life.     

Working from an earlier discovery of Charpentier’s, chemists Emmanuelle Charpentier and Jennifer Doudna—winners of the 2020 Nobel Prize in Chemistry—re-created and then reprogrammed the so-called “genetic scissors” of a species of DNA-cleaving bacteria ______blank a tool that is revolutionizing the field of gene technology.

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

The artistic talents of Barbara Chase-Riboud, most known for her 1979 historical novel Sally Hemings and the conversation it inspired, ______blank limited to the realm of prose: she first excelled in sculpture, where her affinity for bronze—a material she described as “timeless” due to its use across eras and cultures—became part of her artistic identity.

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

In a 2016 study, Eastern Washington University psychologist Amani El-Alayli found that, among the study participants who experienced frisson (a physiological response akin to goosebumps or getting the chills) while listening to music, there was one personality trait that they scored particularly ______blank openness to experience.

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

African American Percy Julian was a scientist and entrepreneur whose work helped people around the world to see. Named in 1999 as one of the greatest achievements by a US chemist in the past hundred years, ______blank led to the first mass-produced treatment for glaucoma.

The radiation that ______blank during the decay of radioactive atomic nuclei is known as gamma radiation.

Archaeologists have estimated that the pre-Columbian Native American city of Cahokia, located across the Mississippi River from modern-day St. Louis, Missouri, had as many as 20,000 inhabitants in the year 1150 ______blank it one of the largest cities in North America at the time.

In 2008, two years after the death of science fiction writer Octavia Butler, the Huntington Library in ______blank received a collection of more than 8,000 items, including Butler’s private notes, research materials, manuscripts, photos, and drawings. Today, the Octavia E. Butler Collection is one of the most researched archives at the library.

When external forces are applied to common glass made from silicates, energy builds up around minuscule defects in the material, resulting in fractures. Recently, engineer Erkka Frankberg of Tampere University in Finland used the chemical ______blank to make a glassy solid that can withstand higher strain than silicate glass can before fracturing.