According to the research presented in the Critical Thinking box on smoking and psychological disorders, nicotine is implicated in psychological disorders because:

A. nicotine affects many of the same neurotransmitters and brain areas that are involved in mental disorders.
B. people with schizophrenia or depression tend to have abnormally high threshold levels for responding to nicotine.
C. nicotine is a toxic chemical that suppresses the release of dopamine and other neurotransmitters that are necessary for normal mental functioning.
D. people with psychological disorders tend to absorb more nicotine from cigarettes than other people, making it easier for them to become addicted to nicotine.

Ais a group of people living and working under a set of rules and traditions.

It is widely assumed that people need to engage in intellectual activities such as solving crossword puzzles or mathematics problems in order to maintain mental sharpness as they age. in fact, however, simply talking to other people—that is, participating in social interaction, which engages many mental and perceptual skills—suffices. evidence to this effect comes from a study showing that the more social contact people report, the better their mental skills. which of the following, if true, most seriously weakens the force of the evidence cited? (a) as people grow older, they are often advised to keep exercising their physical and mental capacities in order to maintain or improve them. (b) many medical conditions and treatments that adversely affect a person's mental sharpness also tend to increase that person's social isolation. (c) many people are proficient both in social interactions and in solving mathematical problems. (d) the study did not itself collect data but analyzed data bearing on the issue from prior studies. (e) the tasks evaluating mental sharpness for which data were compiled by the study were more akin to mathematics problems than to conversation.

The country at the southern tip of africa is