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: Ends and Means (an Enquiry Into the Nature of Ideals and Into the Methods Employed for Their Realization) is a book of essays written by Aldous Huxley. 
 Question: Which author wrote the novel titled Ends and Means?
[A]: aldous huxley


[Q]: Context: How quickly is the human population growing? If we look at worldwide human population growth from 10,000 BCE through today, our growth looks like exponential growth. It increased very slowly at first, but later grew faster and faster as the population increased in size ( Figure 1.1). And recently, the human population has increased at a faster pace than ever before. It has taken only 12 years for the worlds population to increase from six billion to seven billion. Considering that in the year 1804, there were just one billion people, and in 1927, there were just two billion people (thats 123 years to increase from 1 to 2 billion), the recent increase in the human population growth rate is characteristic of exponential growth. Does this mean there are unlimited resources? Worldwide human population growth from 10,000 BCE through today. On the other hand, if you look at human population growth in specific countries, you may see a different pattern. On the level of a country, the history of human population growth can be divided into five stages, as described in Table 1.1. Some countries have very high birth rates, in some countries the growth rate has stabilized, and in some countries the growth rate is in decline. Stage 1 2 3 4 5 Description Birth and death rates are high and population growth is stable. This occurred in early human history. Significant drop in death rate, resulting in exponential growth. This occurred in 18th- and 19th-century Eu- rope. Population size continues to grow. Birth rates equal death rates and populations become stable. Total population size may level off. The United Nations and the U.S. Census Bureau predict that by 2050, the Earth will be populated by 9.4 billion people. Other estimates predict 10 to 11 billion. There are two different beliefs about what type of growth the human population will undergo in the future: 1. Neo-Malthusians believe that human population growth cannot continue without destroying the environment, and maybe humans themselves. 2. Cornucopians believe that the Earth can give humans a limitless amount of resources. They also believe that technology can solve problems caused by limited resources, such as lack of food. The Cornucopians believe that a larger population is good for technology and innovation. The 5-stage model above predicts that when all countries are industrialized, the human population will eventually level out. But many scientists and other Neo-Malthusians believe that humans have already gone over the Earths carrying capacity. That means, we may have already reached the maximum population size that can be supported, without destroying our resources and habitat. If this is true, then human overpopulation will lead to a lack of food and other resources. Overpopulation may also lead to increased disease, and/or war. These problems may cause the population of humans to crash. If these issues are not controlled, could the human population go extinct? Which of the above theories makes sense to you? Why? 
 Question: which is the last stage of human population growth?
[A]: total population size may level off.


[Q]: Context: Accumulation and deposition of -amyloid peptides (A) in the brain is a central event in the pathogenesis of Alzheimer's disease (AD). Besides the parenchymal pathology, A is known to undergo active transport across the blood-brain barrier and cerebral amyloid angiopathy (CAA) is a prominent feature in the majority of AD. Although impaired cerebral blood flow (CBF) has been implicated in faulty A transport and clearance, and cerebral hypoperfusion can exist in the pre-clinical phase of Alzheimer's disease (AD), it is still unclear whether it is one of the causal factors for AD pathogenesis, or an early consequence of a multi-factor condition that would lead to AD at late stage. To study the potential interaction between faulty CBF and amyloid accumulation in clinical-relevant situation, we generated a new amyloid precursor protein (APP) knock-in allele that expresses humanized A and a Dutch mutation in addition to Swedish/London mutations and compared this line with an equivalent knock-in line but in the absence of the Dutch mutation, both crossed onto the PS1M146V knock-in background. Introduction of the Dutch mutation results in robust CAA and parenchymal A pathology, age-dependent reduction of spatial learning and memory deficits, and CBF reduction as detected by fMRI. Direct manipulation of CBF by transverse aortic constriction surgery on the left common carotid artery caused differential changes in CBF in the anterior and middle region of the cortex, where it is reduced on the left side and increased on the right side. However these perturbations in CBF resulted in the same effect: both significantly exacerbate CAA and amyloid pathology. Our study reveals a direct and positive link between vascular and parenchymal A; both can be modulated by CBF. The new APP knock-in mouse model recapitulates many symptoms of AD including progressive vascular and parenchymal A pathology and behavioral deficits in the absence of APP overexpression. 
 Question: Which disease the London mutation involved in?
[A]:
alzheimer's disease