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.

Q: Context: To develop clinical rules for the safe and effective use of flumazenil in suspected benzodiazepine overdose. We assembled a retrospective series of 35 consecutive comatose patients admitted between October 1992 and July 1993 to a toxicologic ICU with the presumptive diagnosis of drug overdose. These patients were divided into two groups. Group A (low-risk) patients had a clinical picture compatible with uncomplicated benzodiazepine intoxication (calm, without abnormalities in pulse or blood pressure, lateralizing signs, hypertonia, hyperreflexia, or myoclonus) in the absence of predefined electrocardiographic or clinical signs of tricyclic antidepressant or other proconvulsant overdose, and absence of an available history of long-term benzodiazepine treatment or an underlying seizure disorder. Group B ("non-low risk") comprised all other patients. Efficacy of flumazenil was categorized as complete awakening (with normal level of alertness), partial awakening, or no change in alertness level. The safety of flumazenil was defined on the basis of the absence of seizures or death. In group A (n=4), flumazenil was associated with complete awakening in three patients and partial awakening in one. No seizures were observed. In group B (n=31), flumazenil was associated with complete awakening in 4 patients, partial awakening in 5, and no response in 22. In group B, five seizures occurred. Comatose patients with clinical or ECG criteria thought to contraindicate the use of flumazenil have a reasonably high risk of seizures after administration of this drug. Low-risk patients may be able to receive flumazenil safely, but they may be only a small portion of comatose patients with suspected overdose. 
 Question: Which drug should be used as an antidote in benzodiazepine overdose?

A: flumazenil
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Q: Context: Energy levels (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found. Electrons are tiny, negatively charged particles in an atom that move around the positive nucleus at the center. Energy levels are a little like the steps of a staircase. You can stand on one step or another but not in between the steps. The same goes for electrons. They can occupy one energy level or another but not the space between energy levels. The model in the Figure 1.1 shows the first four energy levels of an atom. Electrons in energy level I (also called energy level K) have the least amount of energy. As you go farther from the nucleus, electrons at higher levels have more energy, and their energy increases by a fixed, discrete amount. Electrons can jump from a lower to the next higher energy level if they absorb this amount of energy. Conversely, if electrons jump from a higher to a lower energy level, they give off energy, often in the form of light. This explains the fireworks pictured above. When the fireworks explode, electrons gain energy and jump to higher energy levels. When they jump back to their original energy levels, they release the energy as light. Different atoms have different arrangements of electrons, so they give off light of different colors. Q: In the atomic model Figure 1.1, where would you find electrons that have the most energy? A: Electrons with the most energy would be found in energy level IV. The smallest atoms are hydrogen atoms. They have just one electron orbiting the nucleus. That one electron is in the first energy level. Bigger atoms have more electrons. Electrons are always added to the lowest energy level first until it has the maximum number of electrons possible. Then electrons are added to the next higher energy level until that level is full, and so on. How many electrons can a given energy level hold? The maximum numbers of electrons possible for the first four energy levels are shown in the Figure 1.1. For example, energy level I can hold a maximum of two electrons, and energy level II can hold a maximum of eight electrons. The maximum number depends on the number of orbitals at a given energy level. An orbital is a volume of space within an atom where an electron is most likely to be found. As you can see by the images in the Figure 1.2, some orbitals are shaped like spheres (S orbitals) and some are shaped like dumbbells (P orbitals). There are other types of orbitals as well. Regardless of its shape, each orbital can hold a maximum of two electrons. Energy level I has just one orbital, so two electrons will fill this energy level. Energy level II has four orbitals, so it takes eight electrons to fill this energy level. Q: Energy level III can hold a maximum of 18 electrons. How many orbitals does this energy level have? A: At two electrons per orbital, this energy level must have nine orbitals. Electrons in the outermost energy level of an atom have a special significance. These electrons are called valence electrons, and they determine many of the properties of an atom. An atom is most stable if its outermost energy level contains as many electrons as it can hold. For example, helium has two electrons, both in the first energy level. This energy level can hold only two electrons, so heliums only energy level is full. This makes helium a very stable element. In other words, its atoms are unlikely to react with other atoms. Consider the elements fluorine and lithium, modeled in the Figure 1.3. Fluorine has seven of eight possible electrons in its outermost energy level, which is energy level II. It would be more stable if it had one more electron because this would fill its outermost energy level. Lithium, on the other hand, has just one of eight possible electrons in its outermost energy level (also energy level II). It would be more stable if it had one less electron because it would have a full outer energy level (now energy level I). Both fluorine and lithium are 
 Question: any atom is most stable when its outermost energy level contains

A: as many electrons as it can hold.
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Q: Context: Christianson syndrome (CS) is caused by mutations in SLC9A6 and is characterized by severe intellectual disability, absent speech, microcephaly, ataxia, seizures, and behavioral abnormalities. The clinical phenotypes of CS and Angelman syndrome (AS) are similar. Differentiation between CS and AS is important in terms of genetic counseling. We report on two children with CS and confirmed mutations in SLC9A6 focusing on neuroimaging findings and review the available literature. Cerebellar atrophy (CA) occurs in approximately 60% of the patients with CS and develops after the age of 12 months. Hyperintense signal of the cerebellar cortex (CbC) is less common, and may be diffuse, patchy, or involve only the inferior part of the cerebellum and is best seen on coronal fluid attenuation inversion recovery images. CA and CbC-hyperintensity are not neuroimaging features of AS. In a child with the phenotype of AS, CA and/or CbC-hyperintensity are rather specific for CS and should prioritize sequencing of SLC9A6. 
 Question: Mutation of which gene is implicated in the Christianson syndrome?

A:
slc9a6
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