Which of the following is correct? A.
When the lungs contract, they fill with air from the atmosphere.

B.
When the heart contracts, it fills with air from the atmosphere.

C.
When the lungs expand, they fill with air from the atmosphere.

D.
When the heart expands, it fills with air from the atmosphere.

Which of the following statements about slavery is not correct? a. slavery was a very profitable industry that build the united states. b. the french were the first to profit from the african slave trade. c. slaves were sold at auction blocks like farm animals. d. slaves were not considered citizens or even people.

How do economists measure the success, or shortcomings, of the economy?

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a study of twenty 4th grade classrooms in which researchers ask the schools to systematically vary the time of day reading is taught, and collect weekly assessments of reading comprehension for each child over a three-month period.the collection of data, by a playground designer hired by the superintendent of schools, about the physical dimensions of school playgrounds, presence of fencing, and the kinds of equipment currently provided.a feasibility study for implementing a year-round school program, focusing on economic issues such a facilities utilization and transportation costs.an analysis of aggregate data comparing statewide high school graduation rates provided by the state department of public instruction, using county tax information.