In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.

Input: Consider Input: Article: Let's pretend we're sailing down the Rhine River on a pleasure boat. The Rhine is one of the main waterways of Germany, and the river traffic is heavy. It's interesting to watch the many boats going up and down the river. But the river traffic is not nearly so interesting as the beautiful scenery along the banks and hillsides. The boat is passing many old castles. We can see people working in the vineyards on the hillsides. There are vineyards as far as the eye can see. Wine from the Rhine Valley is famous all over the world. Suddenly our boat slows down and begins to turn a little. We are coming to a sharp bend in the river. On our right we can see a rocky cliff over 400 feet high. At first it looks quite ordinary, but there is nothing ordinary about it. There are many stories, poems, and songs about the cliff. We are looking at the Lorelei. Then someone on the boat begins to sing in German, the song of the Lorelei. It is a song about a beautiful siren who has lured many sailors to their deaths. The siren is supposed to sit on the rock combing her long golden hair and singing. The sailors who hear her forget to steer , and the current of river hurls their boats on the rocks and dashes them to pieces. Soon other people on the boat begin to sing. The beautiful song adds to special magic to the moment, and you begin to realize why so many people have made this trip down the Rhine to see the rock of the Lorelei.
Question: The most interesting thing to those who are sailing down the Rhine River on a pleasure boat is _ .
Options: (A) to watch many boats going up and down the river (B) to see the beautiful scene along the banks and hillsides (C) to hear a song about beautiful siren (D) to see a beautiful siren combing her golden hair

Output: B

Input: Consider Input: Article: Recent research has claimed that an excess of positive ions in the air can have an ill effect on people's physical or psychological health. What are positive ions? Well, the air is full of ions, electrically charged particles, and generally there is a rough balance between the positive and the negative charged. But sometimes this balance becomes disturbed and a larger proportion of positive ions are found. This happens naturally before thunderstorm, earthquakes when winds are blowing in certain countries. Or it can be caused by a build-up of static electricity indoors from carpets or clothing, or from TV sets, duplicators or computer display screens. When a large number of positive ions are present in the air many people experience unpleasant effects such as headaches, fatigue , excessive anger, and some particularly sensitive people feel sick or even suffer mental disturbance. Animals are also affected, particularly before earthquakes, snakes have been observed to come out, rats to flee from their burrows, dogs howl and cats jump about unaccountably. This has led the US Geographical Survey to fund a network of volunteers to watch animals in an effort to foresee such disasters before they hit vulnerable areas such as California. Conversely, when large numbers of negative ions are present, then people have a feeling of well-being. Natural conditions that produce these large amounts are near the sea, close to waterfalls or fountains, or in any place where water is sprayed, or forms a spray. This probably accounts for the beneficial effect of a holiday by the sea, or in the mountains with streams or waterfalls. To increase the supply of negative ions indoors, some scientists recommend the use of ionisers. They claim that ionisers not only clean and refresh the air but also improve the health of people sensitive to excess positive ions. Of course, there are the detractors, other scientists, who dismiss such claims and are skeptical about negative/positive ion research. Therefore people can only make up their own minds by observing the effects on themselves, or on others, of a negative rich or poor environment. After all it is debatable whether depending on seismic readings to anticipate earthquakes is more effective than watching the cat.
Question: What is an ion according to the passage?
Options: (A) It's a charged particle. (B) It's basically static electricity indoors. (C) It's a balance between the positive and negative charged. (D) It's an ill effect on people's physical and psychological health.

Output: A

Input: Consider Input: Article: The growing popularity of digital reading has encouraged best-selling young Chinese author Han Han to release his new novel on the Internet. Ta De Guo (His Country), of which Han Han has finished only one tenth so far, will be available for paid reading from December 1ston Qidian.com, the online library has announced. Han Han will update the story every day and finish the book before the end of the year. A printed edition will only be produced after all of the content goes online, sources said. To read the entire book, readers will have to pay eight yuan, or 0.08yuanper 1,000 words. This is almost four times the price of an average writer on Qidian.com. Lu Jinbo, a well-known publisher, estimated that a popular writer like Han Han is likely to attract 20 million subscribers. That means this high-school-dropout-turned popular author could bring in 160 million yuan, nearly 40 times as much as he earned in copyright royalties last year. On the 2007 list of Chinese millionaire writers, Han Han ranked 13th with 3.8 million yuan. The richest, Guo Jingming, earned 11 millionyuan. Statistics from China Internet Network Information Center show that there are at least 253 million Internet users in prefix = st1 /China. Such a large-scale Internet population has developed a prosperous industry for online novel writing. Among the many success stories is Zhang Muye, an office worker whose fantasy novel Ghost Blows out the Lightmade him the 19th wealthiest author in 2007. Besides the potential to gain a large readership base, the Internet writers are being recognized professionally. The jury of the Mao Dun Literature Prize, the most prestigious honor for Chinese writers, is considering adding a category for online writers.
Question: According to the passage, online writing is becoming more and more popular mainly because _ .
Options: (A) it's a good way to save paper (B) it's convenient to write online (C) all the online stories are interesting (D) Internet users inChinaare increasing
Output: D