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 outcome of viral infection depends on the interplay between host factors and the environment.

SOLUTION: background

PROBLEM: Mice were orally treated for 9 consecutive days starting on the day of infection with daily ATA doses of 50 and 100 mmol/kg.

SOLUTION: method

PROBLEM: Plant molecular pharming has emerged as a reliable platform for recombinant protein expression providing a safe and low-cost alternative to bacterial and mammalian cellsbased systems.

SOLUTION:
background