Given the task definition and input, reply with output. 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.

Article: 2008 sadly saw the worst earthquake in China in over 30 years. The Great Sichuan Earthquake was 8 on the Richter scale and killed around 70,000 people in May, not to mention the tens of thousands who were injured or went missing. On 26thJanuary, 2009, the biggest earthquake in India took the lives of 25,000 people. In the morning, when everybody was enjoying holiday, the earthquake began, It was about 7.5 on the Richter scale. "There is nothing left between the sky and the earth any more. Everything has been pulled down. " said one of the villagers alive. " There is no water, no food and no one has come to help." Nobody died in Pakistan, a country next to India. The City of Lahore was lucky. In Lahore American School, where I was studying, all of the students were safe. They were in the field, so most children didn't feel anything. The earthquake was felt by the teachers that were on the second floor. However, though Mrs Young was also on the second floor, she didn't feel anything. She didn't know what happened until a teacher told her about it. Those teachers who were on the other floors had different feelings. Mr Emond, the maths teacher from Australia, said that when the earthquake started he thought there was something wrong with him, but then another teacher said that it was an earthquake. After those words Mr Emond felt better. Mrs Davis and Mr Frost didn't feel anything either. My mother didn't feel anything. She didn't even know that it was an earthquake till she saw a shaking light. My dad saw the computer shaking and then he looked out of the window and saw many people going out.
Question: People use Richter scale to tell _
Options: (A) where the earthquake takes place (B) when the earthquake takes place (C) how serious the earthquake is (D) how long the earthquake lasts
C