Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Q: 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.

A: complete the following sentence. as molecules are moving against their concentration gradients, active transport cannot occur without __________.
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Q: With an ageing population and improving cancer therapies, the two most common benign and malignant bone diseases, osteoporosis and bone metastases, will continue to affect an increasing number of patients. Our expanding knowledge of the molecular processes underlying these conditions has resulted in novel bone targets that are currently being explored in clinical trials. Clearly, the approval of denosumab, a monoclonal antibody directed against RANKL, has just marked the beginning of a new era for bone therapy with several additional new therapies lining up for clinical approval in the coming years. Potential agents targeting the osteoclast include cathepsin K, currently in phase 3 trials, and src inhibitors. Amongst anabolic agents, inhibitors of the Wnt-inhibitor sclerostin and dickkopf-1 are promising in clinical trials. Here, we will provide a comprehensive overview of the most promising agents currently explored for the treatment of bone diseases.

A: To the ligand of which receptors does Denosumab (Prolia) bind?
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Q: The French Revolution broke out in 1789. At the time France was in a crisis. The government was badly run and people's lives were miserable. King Louis XIV tried to control the national parliament and raise more taxes. But his effort failed. He ordered his troops to Versailles. The people thought that Louis intended to put down the Revolution by force. On July 14, 1789, they stormed and took the Bastille, where political prisoners were kept. Ever since that day, July 14 has been the French National Day. Louis tried to flee the country in 1792, to get support from Austria and Prussia. However, he was caught and put in prison. In September 1792, the monarchy was abolished _ . In the same year, Louis was executed. A few months later his wife, Marie also had her head cut off. The Revolution of France had frightened the other kings of Europe. Armies from Austria and Prussia began to march against France. The French raised republican armies to defend the nation. The Revolution went through a period of terror. Thousands of people lost their lives. In the end, power passed to Napoleon Bonaparte.

A:
What's this passage about?
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