单项选择题
A．He needs another job as research assistant. B．He asked Professor Williams for assistance. C．He assists Professor Williams with his teaching. D．He is doing research with Professor Williams.
A．The cruel master. B．The man in the kitchen. C．The pet bird. D．The fourth chicken.
A．Some of their prisoners are allowed to study or work outside prisons. B．Most of their prisoners are expected to work. C．Their prisoners are often sent to special centers for skill training. D．Their prisoners are allowed freedom to visit their families.