Around how long did it take for Marco polo to travel to china​

An economic term that describes happiness and its hard to measure in numbers is

Identify the example of when situation and time are key to assessing risk of harm in a research study: a study on the efficacy of a behavioral intervention for smoking cessation involves both adults and teenagersasking women if they have had an abortionresearch on the prevalence of hiv-infected individuals in communitiesa survey about sexually transmitted diseases

17 points! ! (explain your answer)