Name two other methods through which the primary data can be collected apart from direct personal investigation.

Using complete sentences, describe the central economic problem facing all humans. why does this require people to make choices? how can this result in opportunity costs?

Computer models can scientists predict weather. some computer models can show the predicted path of hurricanes. what other events could a computer model warn us of? a) undersea earthquakes , tornadoes, and avalanches b) tornadoes c) avalanches d) undersea earthquakes

As water is cooled from 4 c to 0 c its density