This paper describes a question answering system and its various modules to solve definition, factoid and list questions defined in the TREC12 Main task. In particular, we tackle the factoid QA task by Event-based Question Answering. Each QA event comprises of elements describing different facets like time, location, object, action etc. By analyzing the external knowledge from pre-retrieved TREC documents, Web documents, WordNet and Ontology to discover the QA event structure, we explore the inherent associations among QA elements and then obtain the answers. There are three subsystems working parallel to handle definition, factoid, and list questions separately. We highlight the shared modules, fine-grained named entity recognition, anaphora resolution and canonicalization co-reference resolution, among the three subsystems as well.