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:
Pathological aging
Explanation:
Pathological aging is usually associated with older adults; it is a form of aging that is characterized by severe long term and short term memory loss. A feature of pathological aging is the increase in cerebrovascular and neurodegenerative disorders. Another feature of pathological aging is synaptic and neuronal loss. Individuals begin to forget things that they originally do not forget, like forgetting their driving routes.
Pretty sure it is d, The exact size of population
Dowager Empress Cixi was very fond of the Boxer Rebellion because she saw this as a chance for them to push the foreigners away. However it cause foreign attacks on Chinese forts.
