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.

Let me give you an example: Article: Homework can put you in a bad mood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Question: Researchers did experiments on kids in order to find out _ .
Options: (A) how they really feel when they are learning (B) whether mood affects their learning ability (C) what methods are easy for kids to learn (D) the relationship between sadness and happiness
The answer to this example can be: B
Here is why: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment. So, B is the correct answer.

OK. solve this:
Article: If we say the four great inventions (Gunpowder,Compass,Paper and Art of Printing) reflected ancient China's scientific achievements,then Zhaozhou Stone Bridge perfectly represented one of the greatest contributions to ancient China's bridge building.Nobody was unfamiliar with the stone bridge full of legends and vivid folk stories. The ancient Zhaozhou stone bridge started to be built in 590 during the Sui Dynasty (581~618) and established in 608.The pioneer for building the bridge was Li Chun who overcame unimaginable difficulties,undergoing all hardships.The location of the bridge is in Zhao County south,Hebei Province.It lay across the Xiaoshui River,far away from the mountains that provided rocky materials.In ancient times,it was such a busy,deep and wide river that could be used as an important carriage to transport heavy rocks and other materials.As we know,no train,no lifting machine could be used to move granite blocks to the construction site.As an intelligent stonemason and engineer,Li Chun worked out his plan and design all from his own direct observation and investigation.It took his whole life-time in completing the great historical project inChina.Nowadays it is not only a historical remarkable model of architecture,but also a brilliant Chinese cultural crystallization of wisdom. The entire length of the bridge is 50.82 meters with 10 meters width.The whole stone bridge looks like a big bow,the span of which is 37.02 meters,and its height from the top to the surface of water at a regular position is 7.23 meters.The bridge arch seems to be moving smoothly and flatly.The whole arch consists of 28 big granite blocks connected each other tightly together.On both end sides of the general arch there are 4 smaller arches,2 of which on one side,the other 2 on the other side.The smaller arches could be used to decrease the weight of the bridge and save stone materials,and help flood get through easily,which seems to be much prettier.Such a hard-thinking and careful consideration of the engineering article is really a model of design and layout.The span was much wider than the other stone bridge in ancient times all over China. Today Zhaozhou Stone Bridge is one of international cultural relics and perfectly protected and preserved by the concerned administration of China.
Question: The best title of this passage is _ .
Options: (A) Great engineer in ancient China (B) Zhaozhou stone bridge (C) Four great inventions (D) How to build a bridge
Answer:
B