Given the task definition and input, reply with output. In this task, you will be presented with a context from an academic paper and a question separated with a
. You have to answer the question based on the context.

. Grammatically correct text is needed as the starting point for inserting artificial errors, and we used two different sources: 1) the corrected version of the same FCE training set on which the system is trained (450K tokens), and 2) example sentences extracted from the English Vocabulary Profile (270K tokens).
Question: Which languages are explored in this paper?
English