instruction:
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?). 
question:
and transmission electronic microscopy revealed the presence of an enveloped virus morphologically compatible with a coronavirus isolated in the cultures.
answer:
method


question:
responses to the severe acute respiratory syndrome ( SARS ) outbreak in 2003 and the Middle East respiratory syndrome ( MERS ) outbreak in 2015 had completely different outcomes.
answer:
background


question:
with few exceptions ( e.g. , explicitly delayed self-repressors and simple models of specific organisms ' circadian clocks ).
answer:

background