Models are used in scientific research in order to:. a. determine the best research design for testing a hypothesis b. study systems that would be too complicated or too large to manipulate c. acquire research grant money from rich donors d. study systems that would be too expensive to manipulate

Which of the following areas have the highest population density? a) quebecb) united statesc) californiad) new york city

Physical features of central america look at the map above which of the following is true

Tides are caused by a differences in the gravitational force of the sun at different points on earth. differences in the gravitational force of the moon at different points on earth differences in earth’s gravitational field strength at different points on earth’s surfac fluctuations in the gravitational attraction between earth and the moon.