9.A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.

　　The researcher's conclusion depends on which of the following assumptions？

　　（A） High immune-system activity protects against mental illness better than normal immune-system activity does.

　　（B） Mental illness is similar to physical disease in its effects on body system.

　　（C） People with high immune-system activity cannot develop mental illness.

　　（D） Mental illness does not cause people's immune-system activity to decrease.

　　（E） Psychological treatment of mental illness is not as effective as is medical treatment.

　　10.The program to control the entry of illegal drugs into the country was a failure in 1987. If the program had been successful， the wholesale price of most illegal drugs would not have dropped substantially in 1987.

　　The argument in the passage depends on which of the following assumptions？

　　（A） The supply of illegal drugs dropped substantially in 1987.

　　（B） The price paid for most illegal drugs by the average consumer did not drop substantially in 1987.

　　（C） Domestic production of illegal drugs increased at a higher rate than did the entry of such drugs into the country.    （D） The wholesale price of a few illegal drugs increased substantially in 1987.

　　（E） A drop in demand for most illegal drugs in 1987 was not the sole cause of the drop in their wholesale price.