In this task, you are given a sentence from the research paper and your task is to classify the given sentence into the following categories: Background (Why is this problem important? What relevant works have been created before? What is still missing in the previous works? What are the high-level research questions? How might this help other research or researchers?), Purpose (What specific things do the researchers want to do? What specific knowledge do the researchers want to gain? What specific hypothesis do the researchers want to test?), Method (How did the researchers do the work or find what they sought? What are the procedures and steps of the research?), or Finding (What did the researchers find out? Did the proposed methods work? Did the thing behave as the researchers expected?). 

Example Input: has been approved to treat inflammatory-related diseases , such as pancreatitis.
Example Output: background

Example Input: The global therapeutic monoclonal antibody market was valued at approximately US$ 115.2 billion in 2018 and is expected to generate revenue of $ 150 billion by the end of 2019 and $ 300 billion by 2025.
Example Output: background

Example Input: All the proteins were expressed and purified using a GST-fusion expression system in Escherichia coli.
Example Output:
method