Answer: D) Mandarin
Explanation: The language spoken by the most people in the world today is Mandarin, also known as Standard Chinese or Putonghua. It is the official language of China, Taiwan, and Singapore, and it is also widely spoken in other countries such as Malaysia, Indonesia, and the Philippines. According to Ethnologue, a database of world languages, Mandarin has approximately 1.1 billion speakers worldwide. Therefore, the correct answer is D.