1. A virtual pet system, comprising: a virtual pet client and a question and answer (Q&A) server, wherein the virtual pet client is adapted to receive a sentence in natural language and send the sentence to the Q&A server; the Q&A server is adapted to receive the sentence in natural language, process the sentence through natural language comprehension, generate an answer in natural language based on a result of natural language comprehension and reasoning knowledge, and send the answer in natural language to the virtual pet client.