Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: Stress is the force applied to an object. In geology, stress is the force per unit area that is placed on a rock. Four types of stresses act on materials. A deeply buried rock is pushed down by the weight of all the material above it. Since the rock cannot move, it cannot deform. This is called confining stress. Compression squeezes rocks together, causing rocks to fold or fracture (break) (Figure 1.1). Compression is the most common stress at convergent plate boundaries. Stress caused these rocks to fracture. Rocks that are pulled apart are under tension. Rocks under tension lengthen or break apart. Tension is the major type of stress at divergent plate boundaries. When forces are parallel but moving in opposite directions, the stress is called shear (Figure 1.2). Shear stress is the most common stress at transform plate boundaries. Shearing in rocks. The white quartz vein has been elongated by shear. When stress causes a material to change shape, it has undergone strain or deformation. Deformed rocks are common in geologically active areas. A rocks response to stress depends on the rock type, the surrounding temperature, the pressure conditions the rock is under, the length of time the rock is under stress, and the type of stress. Rocks have three possible responses to increasing stress (illustrated in Figure 1.3): elastic deformation: the rock returns to its original shape when the stress is removed. plastic deformation: the rock does not return to its original shape when the stress is removed. fracture: the rock breaks. Under what conditions do you think a rock is more likely to fracture? Is it more likely to break deep within Earths crust or at the surface? What if the stress applied is sharp rather than gradual? At the Earths surface, rocks usually break quite quickly, but deeper in the crust, where temperatures and pressures are higher, rocks are more likely to deform plastically. Sudden stress, such as a hit with a hammer, is more likely to make a rock break. Stress applied over time often leads to plastic deformation. Click image to the left or use the URL below. URL: 
 Question: rocks that are pulled apart are under
tension

Context: A personal journey into the heart of the Killing FieldsOne of the most harrowing and compelling personal documentaries of our time, ENEMIES OF THE PEOPLE exposes for the first time the truth about the Killing Fields and the Khmer Rouge who were behind Cambodias horrific genocide. More than simply an inquiry into Cambodias experience, however, ENEMIES OF THE PEOPLE is a profound meditation on the nature of good and evil, shedding light on the capacity of some people to do terrible things and for others to forgive them.Winner of a dozen top documentary festival awards, including a Special Jury Prize at Sundance and the Grand Jury Award at the Full Frame Documentary Festival, this is a riveting film that takes audiences as close to witnessing evil as they are ever likely to get. It is also a personal journey into the heart of darkness by journalist/filmmaker Thet Sambath, whose family was wiped out in the Killing Fields, but whose patience and discipline elicits unprecedented on-camera confessions from perpetrators at all levels of the Khmer Rouge hierarchy. This is investigative journalism of the highest order.In 1974, Thet Sambaths father became one of the nearly two million people who were murdered by the Khmer Rouge when he refused to give them his buffalo. Sambaths mother was forced to marry a Khmer Rouge militiaman and died in childbirth in 1976, while his eldest brother disappeared in 1977. Sambath himself escaped Cambodia at age 10 when the Khmer Rouge fell in 1979.Fast forward to 1998, and Sambath, now a journalist, got to know the children of some senior Khmer Rouge cadre and gradually earned their trust. Then, for a decade, he spent weekends visiting the home of the most senior surviving leader, Nuon Chea, aka Brother Number Two under Pol Pot. But he never used to say anything different from what he told Western journalists, says Sambath, I was low-ranking, I knew nothing, I am not a killer. Then one day he said to me Sambath, I trust you, you are the person I would like to tell my story to. Ask me what you want to know. For the next five years he told me the truth, as he saw it, including all the details of killing.Sambath also won the confidence of lower-level Khmer Rouge soldiers, now ordinary fathers and grandfathers, who demonstrated to him how they slit peoples throats. For these murderers, it was the first time they admitted what they had done. He taped their interactions and discussions about the killings, and together with British documentarian Rob Lemkin they created this landmark film.For Sambath, it has been an ongoing, lifelong personal journey to discover what was behind such horror; he neglected both his family and his own happiness in the search for truth with hope of reconciliation. ENEMIES OF THE PEOPLE is at once a cinematically beautiful, chillingly insightful, and deeply personal piece of documentary filmmaking. 
 Question: How many Cambodians died during the rule of Khmer Rouge?
nearly two million

Context: When developing novel microbicide products for the prevention of HIV infection, the preclinical safety program must evaluate not only the active pharmaceutical ingredient but also the product itself. To that end, we applied several relatively standard toxicology study methodologies to female sheep, incorporating an assessment of the pharmacokinetics, safety, tolerability, and local toxicity of a dapivirine-containing human vaginal ring formulation (Dapivirine Vaginal Ring-004). We performed a 3-month general toxicology study, a preliminary pharmacokinetic study using drug-loaded vaginal gel, and a detailed assessment of the kinetics of dapivirine delivery to plasma, vaginal, and rectal fluid and rectal, vaginal, and cervical tissue over 28 days of exposure and 3 and 7 days after removal of the ring. The findings of the general toxicology study supported the existing data from both preclinical and clinical studies in that there were no signs of toxicity related to dapivirine. In addition, the presence of the physical dapivirine ring did not alter local or systemic toxicity or the pharmacokinetics of dapivirine. Pharmacokinetic studies indicated that the dapivirine ring produced significant vaginal tissue levels of dapivirine. However, no dapivirine was detected in cervical tissue samples using the methods described here. Plasma and vaginal fluid levels were lower than those in previous clinical studies, while there were detectable dapivirine levels in the rectal tissue and fluid. All tissue and fluid levels tailed off rapidly to undetectable levels following removal of the ring. The sheep represents a very useful model for the assessment of the safety and pharmacokinetics of microbicide drug delivery devices, such as the vaginal ring. 
 Question: Which infection can be prevented with Dapivirine?

hiv