The answer is b just did it in edg 2021
Serfs paid the owner of the land (in the form of labor) to be able to live on the land and have protection, if the serf were to leave. It was usually an unspoken agreement that they serf would stay on the land. If you still need further information you might find some on http://www.thefinertimes.com/Middle-Ages/serfs-in-the-middle-ages.html
Answer:
c. voluntary participation
Explanation:
In the context, Professor Smith conducts a research in the dating behaviors of her college students. She wishes to track the students dating behavior through their entire college careers. So on her first class she explains her research work to the students and does the survey during the class.
Thus in this case, the research has an effect on the voluntary participation of the college students as all the students present in her class was given the survey to complete and they were not asked for their voluntary participation in he survey.
Hence the correct option is (c).
