In this task, you're expected to write answers to questions involving multiple references to the same entity. The answer to the question should be unambiguous and a phrase in the paragraph. Most questions can have only one correct answer.

Passage: Increasing tourist and commercial interest in petrified wood during the late 19th century began to alarm residents of the region. In 1895, the Arizona Territorial Legislature asked the U.S. Congress to create a petrified forest national park. Although this first attempt failed, in 1906 the Antiquities Act signed by President Theodore Roosevelt was used to create the Petrified Forest National Monument. Between 1934 and 1942, the federal Civilian Conservation Corps built road, trails, and structures in the monument, and the government acquired additional land in the Painted Desert section. The monument became a national park in 1962. Six years after the signing of the Wilderness Act in 1964 by President Lyndon B. Johnson, wilderness areas (where human activity is limited), were designated in the park. In 2004, President George W. Bush signed a bill authorizing the eventual expansion of the park from 93,353 acres (about 146 mi2 or 378 km2) to 218,533 acres (about 341 mi2 or 884 km2). Theft of petrified wood is still a problem. Despite a guard force of seven National Park Service rangers, fences, warning signs, and the threat of a $325 fine, an estimated 12 short tons (11,000 kg) of the fossil wood is stolen from the Petrified Forest every year.Jessee Walter Fewkes, the first archeologist to visit Puerco Ruin, predicted in the late 19th century that it would yield many artifacts. Conservationist John Muir conducted the first excavations of the ruin in 1905–06. Although he did not publish his findings, he urged the federal government to preserve Petrified Forest. Professional archeological work in the park began in the early 20th century when Walter Hough conducted excavations at Puerco Ruin and other sites.  In 1919, a phytosaur skull was discovered near Blue Mesa in the Petrified Forest and sent to the Museum of Paleontology in Berkeley, California.  In 1921, Annie Alexander, founder of the museum, visited Blue Mesa to collect more of the phytosaur and other specimens; this led to further excavations by paleontologist Charles Camp.  Since then, more than 250 fossil sites have been documented in the park. In the 1930s, the Civil Works Administration funded research in the park by archeologists H.P. Mera and C.B. Cosgrove. A National Park Service resurvey of the Petrified Forest in the early 1940s identified most of the large sites with stone ruins, and subsequent surveys since 1978 have identified a total of more than 600 artifact sites, many of them small. Research in paleontology and archeology continues at the park in the 21st century. 
Question: Who urged the federal government to preserve Petrified Forest?
John Muir.

Passage: In Depression-era North Carolina, George Pemberton is an ambitious timber baron who meets Serena Shaw, a young woman with a sad past. He falls in love with her, they marry, and Serena comes with George to his land. There, she starts taking control of things, pressuring and questioning George, while remaining affectionate towards him.
George's business partner Buchanan feels threatened by her, as she begins to exceed his authority. Things grow worse between George and Buchanan, and Buchanan strikes a deal with the local sheriff, who wants to buy George's land to make a park. George is hurt by Buchanan's betrayal, and Serena convinces George that Buchanan was never his friend.
The next day, they both go shooting alone from the group attempting to flush out a bear. After some snide remarks from Buchanan, George contemplates killing him only to hesitate and be seen by Buchanan. As Buchanan cocks his rifle, George fires first and shoots him in the chest. Campbell, George's worker, witnesses the murder, but denies it when Sheriff McDowell inquires. The death is ruled an accident. Serena consoles George and justifies his actions.
One day, he sees his illegitimate son, Jacob, posing with his mother, Rachel, for a picture. He feels responsible for the boy, and since Rachel never asked for anything, he begins giving sums of money in envelopes to her for Jacob. Serena remains unaware of this, though she does consider Rachel and the baby a threat.
One day, an accident occurs in the forest and Galloway, a mysterious worker, loses his hand to an axe swing. Serena rushes to help him and uses a belt as a tourniquet to stop the bleeding which saves his life. Having problems with her pregnancy, Serena and George rush to the hospital after Serena experiences heavy bleeding and pain. She miscarries. They learn that she can never again bear children. Things continue to grow worse, and Rachel's baby becomes more obvious to Serena. 
Question: Whose death is ruled an accident?
Buchanan.

Passage: Jo Elizabeth Stafford (November 12, 1917 – July 16, 2008) was an American traditional pop music singer and occasional actress, whose career spanned five decades from the late 1930s to the early 1980s. Admired for the purity of her voice, she originally underwent classical training to become an opera singer before following a career in popular music, and by 1955 had achieved more worldwide record sales than any other female artist. Her 1952 song "You Belong to Me" topped the charts in the United States and United Kingdom, the record becoming the first by a female artist to reach number one on the U.K. Singles Chart.
Born in Coalinga, California, Stafford made her first musical appearance at age twelve. While still at high school she joined her two older sisters to form a vocal trio named The Stafford Sisters, who found moderate success on radio and in film. In 1938, while the sisters were part of the cast of Twentieth Century Fox's production of Alexander's Ragtime Band, Stafford met the future members of The Pied Pipers and became the group's lead singer. Bandleader Tommy Dorsey hired them in 1939 to perform back-up vocals for his orchestra.
In addition to her recordings with the Pied Pipers, Stafford featured in solo performances for Dorsey. After leaving the group in 1944, she recorded a series of pop standards for Capitol Records and Columbia Records. Many of her recordings were backed by the orchestra of Paul Weston. She also performed duets with Gordon MacRae and Frankie Laine. Her work with the United Service Organizations (USO) giving concerts for soldiers during World War II earned her the nickname "G.I. Jo". Starting in 1945, Stafford was a regular host of the National Broadcasting Company (NBC) radio series The Chesterfield Supper Club and later appeared in television specials—including two series called The Jo Stafford Show, in 1954 in the U.S. and in 1961 in the U.K. 
Question: Who did Tommy Dorsey hire to perform back-up vocals?

The Pied Pipers.