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.
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Question: Context: 51827 Laurelclark (2001 OH38) is an asteroid named for astronaut Laurel Clark, who was killed in the STS-107 (Columbia) space shuttle reentry disaster on February 1, 2003. 
 Question: Whom is 51827 Laurelclark named after?

Answer: laurel clark


Question: Context: During active transport, molecules move from an area of low concentration to an area of high concentration. This is the opposite of diffusion, and these molecules are said to flow against their concentration gradient. Active transport is called "active" because this type of transport requires energy to move molecules. ATP is the most common source of energy for active transport. As molecules are moving against their concentration gradients, active transport cannot occur without assistance. A carrier protein is always required in this process. Like facilitated diffusion, a protein in the membrane carries the molecules across the membrane, except this protein moves the molecules from a low concentration to a high concentration. These proteins are often called "pumps" because they use energy to pump the molecules across the membrane. There are many cells in your body that use pumps to move molecules. For example, your nerve cells (neurons) would not send messages to your brain unless you had protein pumps moving molecules by active transport. The sodium-potassium pump ( Figure 1.1) is an example of an active transport pump. The sodium-potassium pump uses ATP to move three sodium (Na+ ) ions and two potassium (K+ ) ions to where they are already highly concentrated. Sodium ions move out of the cell, and potassium ions move into the cell. How do these ions then return to their original positions? As the ions now can flow down their concentration gradients, facilitated diffusion returns the ions to their original positions either inside or outside the cell. 
 Question: which statement is true concerning active transport?

Answer: during active transport, molecules move from an area of low concentration to


Question: Context: The immune system is the body system that fights to protect the body from specific pathogens. It has a special response for each type of pathogen. The immune systems specific reaction to a pathogen is called an immune response. The immune system is shown in Figure 21.13. It includes several organs and a network of vessels that carry lymph. Lymph is a yellowish liquid that normally leaks out of tiny blood vessels into spaces between cells in tissues. When inflammation occurs, more lymph leaks into tissues, and the lymph is likely to contain pathogens. Immune system organs include bone marrow, the thymus gland, the spleen, and the tonsils. Each organ has a different job in the immune system. Bone marrow is found inside many bones. Its role in the immune system is to produce white blood cells called lymphocytes. The thymus gland is in the chest behind the breast bone. It stores some types of lymphocytes while they mature. The spleen is in the abdomen below the lungs. Its job is to filter pathogens out of the blood. The two tonsils are located on either side of the throat. They trap pathogens that enter the body through the mouth or nose. Lymph vessels make up a circulatory system that is similar to the blood vessels of the cardiovascular system. However, lymph vessels circulate lymph instead of blood, and the heart does not pump lymph through the vessels. Lymph that collects in tissues slowly passes into tiny lymph vessels. Lymph then travels from smaller to larger lymph vessels. Muscles around the lymph vessels contract and squeeze the lymph through the vessels. The lymph vessels also contract to help move the lymph along. Eventually, lymph reaches the main lymph vessels, which are located in the chest. From these vessels, lymph drains into two large veins of the cardiovascular system. This is how lymph returns to the blood. Before lymph reaches the bloodstream, it passes through small oval structures called lymph nodes, which are located along the lymph vessels. Figure 21.14 shows where some of the bodys many lymph nodes are concentrated. Lymph nodes act like filters and remove pathogens from lymph. A lymphocyte is the type of white blood cell involved in an immune system response. You can see what a lymphocyte looks like, greatly magnified, in Figure 21.15. Lymphocytes make up about one quarter of all white blood cells, but there are trillions of them in the human body. Usually, fewer than half of the bodys lymphocytes are in the blood. The majority are in the lymph, lymph nodes, and lymph organs. There are two main types of lymphocytes, called B cells and T cells. Both types of lymphocytes are produced in bone marrow. They are named for the sites where they grow and mature. The B in B cells stands for bone marrow, where B cells mature. The T in T cells stands for thymus gland, where T cells mature. Both B cells and T cells must be switched on in order to fight a specific pathogen. Once this happens, they produce an army of cells that are ready to fight that particular pathogen. How can B and T cells recognize specific pathogens? Pathogens have unique antigens, often located on their cell surface. Antigens are proteins that the body recognizes either as self or nonself. Self antigens include those found on red blood cells that determine a persons blood type. Generally, the immune system doesnt respond to self antigens. Nonself antigens include those found on bacteria, viruses, and other pathogens. Nonself antigens are also found on other cells, such as pollen cells and cancer cells. It is these antigens that trigger an immune response. There are two different types of immune responses. Both types involve lymphocytes. However, one type of response involves B cells. The other type involves T cells. B cells respond to pathogens in the blood and lymph. Most B cells fight infections by making antibodies. An antibody is a large, Y-shaped molecule that binds to an antigen. Each antibody can bind with just one specific type of antigen. The antibody and antigen fit together like a lock and key. You can see how this works in Figure 21.16. The antibody in 
 Question: __organ in the abdomen that filters pathogens out of the blood

Answer:
spleen