Billy tapped the ruler and it made a funny noise. billy heard the sound because the ruler vibrated molecules back and forth. a) the air b) his ear c) the table d) his finger

Which revelation resulted from the observation of the spectrum of different galaxies? a. there were more galaxies whose spectrum was blueshifted b. there were no galaxies whose spectrum was redshifted c. there were more galaxies whose spectrum was redshifted d. there were no galaxies whose spectrum was blueshifted

The economies of nordon could be described a. unable to use rich resources b. struggling but diverse c. dependent on one product d. healthy and diverse

At which boundary does subduction stop occurring, resulting in a mountain range?