TASK DEFINITION: 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?). 
PROBLEM: The goal of this study was to define the role of the classical complement activation pathway in the progression of pathology in the 3xTg mouse that develops tangles in addition to fibrillar plaques ( more closely reflecting human AD pathology ) and to assess the influence of complement in a model of AD with a higher level of complement hemolytic activity.

SOLUTION: purpose

PROBLEM: purification , and characterization of vaccine protective antigens in veterinary vaccines was also identified as a priority.

SOLUTION: finding

PROBLEM: Purpose : COVID-19 ( coronavirus disease 2019 ) is a public health emergency of international concern.

SOLUTION:
background