The united states is considered to have a high standard of living because .

Which two statements are true about a system? 1. a system is a group of objects analyzed as one unit. 2. energy that moves across system boundaries is conserved. 3. there’s only one way to define the boundaries of a system. 4. all systems are made by humans.

What did pavlov initially notice about the animals in his original research after conditioning took place?

Why did the following change occur? the snow that covered the ground all winter began to melt tempatures rose and flowers started to bloom