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: based on systematic literature reviews and expert consensus.
Example Output: background

Example Input: the onset of severe acute respiratory syndrome coronavirus ( SARS-CoV ) and Middle East respiratory syndrome coronavirus ( MERS-CoV ) have thrust HCoVs into spotlight of the research community due to their high pathogenicity in humans.
Example Output: background

Example Input: We have been using the human Ad12 Syrian hamster cell system for the analysis of epigenetic alterations in Ad12infected cells and in Ad12-induced hamster tumors.
Example Output:
background