If I want to know whether successive cohorts show the same pattern of decline in frequency of close friendships in their 30s, which research design should I use?

Due to senescence, the total size of the brain is ______

Fill in the blank with correct word

Which of the following indicators reflects the possibility of physical dependence?

a. obsessing about a drug b. getting caught with a drug c. abusing a drug d. drug tolerance e. psychosis