Here is a question about this article: The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by
What is the answer to this question: The Avogadro constant is determined to be the ratio between what two factors in the X-ray crystal density method?
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So... the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance

The problem: Answer a question about this article:
Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by cheaper and more reliable heating fuels. As with photovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interest subsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and growth rates have averaged 20% per year since 1999. Although generally underestimated, solar water heating and cooling is by far the most widely deployed solar technology with an estimated capacity of 154 GW as of 2007.
Growth of solar water heating development has averaged how much per year since 1999
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The answer: 20%

Problem: Please answer a question about the following article about Southern Europe:
During the Middle Ages, the Eastern Roman Empire survived, though modern historians refer to this state as the Byzantine Empire. In Western Europe, Germanic peoples moved into positions of power in the remnants of the former Western Roman Empire and established kingdoms and empires of their own.
Who took over the remains of the Western Roman Empire?
A: Germanic peoples

Question: Read this and answer the question

Because the spring equinox was tied to the date of Easter, the Roman Catholic Church considered the seasonal drift in the date of Easter undesirable. The Church of Alexandria celebrated Easter on the Sunday after the 14th day of the moon (computed using the Metonic cycle) that falls on or after the vernal equinox, which they placed on 21 March. However, the Church of Rome still regarded 25 March as the equinox (until 342) and used a different cycle to compute the day of the moon. In the Alexandrian system, since the 14th day of the Easter moon could fall at earliest on 21 March its first day could fall no earlier than 8 March and no later than 5 April. This meant that Easter varied between 22 March and 25 April. In Rome, Easter was not allowed to fall later than 21 April, that being the day of the Parilia or birthday of Rome and a pagan festival.The first day of the Easter moon could fall no earlier than 5 March and no later than 2 April.

Where did the Church of Alexandria place the vernal equinox?
Answer: 21 March

Problem: DST clock shifts sometimes complicate timekeeping and can disrupt travel, billing, record keeping, medical devices, heavy equipment, and sleep patterns. Computer software can often adjust clocks automatically, but policy changes by various jurisdictions of the dates and timings of DST may be confusing.
What do jurisdictions sometimes change that mixes up DST dates and times?
The answer is the following: policy

Input: Article: The armed forces have three branches: Navy, Army and Air Force. They serve primarily as a self-defense force whose mission is to protect the territorial integrity of the country and provide humanitarian assistance and security at home and abroad. As of 2008, the three branches numbered 39,200 active personnel including 7,500 women. Portuguese military expenditure in 2009 was $5.2 billion, representing 2.1 percent of GDP. Military conscription was abolished in 2004. The minimum age for voluntary recruitment is 18 years.

Now answer this question: How many branches make up the Portuguese armed forces?

Output:
three