Which of the following would reduce wind erosion? limiting irrigation cutting down trees planting vegetation clearing away dead leaves

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

How do you tell if someone actually cares about you? and just say they do?

There are two-speed cameras, one in an are where the speed limit is 30 km/h and another where the speed limit is 50 km/h. in which will there be a smaller time interval between the photographs? explain your answer.