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

[Q]: It is unanimously accepted that there is an unmet need for pain medications that are both effective and safe. Unfortunately, no really novel analgesics have been approved over the past three decades. In view of both experimental and clinical evidence of a major role for nerve growth factor (NGF) in the generation and maintenance of a wide range of pain states, drug discovery efforts focusing on the development of anti-NGF agents have aroused particular interest. Several humanized anti-NGF monoclonal antibodies (mAbs) have entered clinical trials as potential analgesics. In this respect, tanezumab is at an advanced stage of clinical development while fulranumab, fasinumab and ABT-110, previously known as PG110, are in early phases of clinical development. This Current Opinion article aims at describing the rationale for targeting NGF for pain, reviewing the analgesic efficacy and safety of anti-NGF agents based on data from fully published studies, conference abstracts, and the US Food and Drug Administration (FDA) website, and discussing the possible future of these agents in managing chronic pain. Anti-NGF mAbs produced significant pain relief and functional improvement in patients with osteoarthritis of the knee and/or hip. Conversely, studies in non-specific lower back pain generated mixed results; overall, this condition appeared to be less responsive to anti-NGF agents than osteoarthritis. Finally, there was no conclusive evidence of the effectiveness of anti-NGF mAbs in some types of chronic visceral or neuropathic pain. Furthermore, these studies raised safety concerns about anti-NGF mAbs. As a class, these drugs may cause or worsen peripheral neuropathies. But the most problematic issue-which prompted the FDA to place studies of these compounds on clinical hold in 2010-was rapid joint destruction leading to joint replacement surgery. The aetiologies of these side effects have been much debated and their pathophysiology is poorly understood. After an Arthritis Advisory Committee meeting held in March 2012, pharmaceutical companies negotiated with the FDA on the conditions for restarting clinical studies. Although the FDA lifted its clinical hold, there remain many unresolved issues about the long-term efficacy and safety of anti-NGF mAbs. While acknowledging that the future of these drugs is unforeseeable, it appears that they may not be the safe and effective painkillers that have been awaited for decades.
[A]: What is the target of tanezumab?


[Q]: The company had an IPO on the NASDAQ in 1996 and in 1997 Europe's largest telecommunications company, Deutsche Telekom, bought a 21.1 percent stake in VocalTec for $48.3 million, in addition to purchasing $30 million in telephony products, services, and support over the following two-and-a-half years.
[A]: What stock exchange is VocalTec associated with?


[Q]: Carbon is a very common ingredient of matter because it can combine with itself and with many other elements. It can form a great diversity of compounds, ranging in size from just a few atoms to thousands of atoms. There are millions of known carbon compounds, and carbon is the only element that can form so many different compounds. Carbon is a nonmetal in group 14 of the periodic table. Like other group 14 elements, carbon has four valence electrons. Valence electrons are the electrons in the outer energy level of an atom that are involved in chemical bonds. The valence electrons of carbon are shown in the electron dot diagram in the Figure 1.1. Q: How many more electrons does carbon need to have a full outer energy level? A: Carbon needs four more valence electrons, or a total of eight valence electrons, to fill its outer energy level. A full outer energy level is the most stable arrangement of electrons. Q: How can carbon achieve a full outer energy level? A: Carbon can form four covalent bonds. Covalent bonds are chemical bonds that form between nonmetals. In a covalent bond, two atoms share a pair of electrons. By forming four covalent bonds, carbon shares four pairs of electrons, thus filling its outer energy level and achieving stability. A carbon atom can form covalent bonds with other carbon atoms or with the atoms of other elements. Carbon often forms bonds with hydrogen. Compounds that contain only carbon and hydrogen are called hydrocarbons. Methane (CH4 ), which is modeled in the Figure 1.2, is an example of a hydrocarbon. In methane, a single carbon atom forms covalent bonds with four hydrogen atoms. The diagram on the left in the Figure 1.2 shows all the shared valence electrons. The diagram on the right in the Figure 1.2, called a structural formula, represents each pair of shared electrons with a dash (-). Methane (CH4 ) Carbon can form single, double, or even triple bonds with other carbon atoms. In a single bond, two carbon atoms share one pair of electrons. In a double bond, they share two pairs of electrons, and in a triple bond they share three pairs of electrons. Examples of compounds with these types of bonds are represented by the structural formulas in the Figure 1.3. Q: How many bonds do the carbon atoms share in each of these compounds? A: In ethane, the two carbon atoms share a single bond. In ethene they share a double bond, and in ethyne they share a triple bond.
[A]:
carbon forms triple bonds with other carbon atoms in the compound named