Groundwater flows through a layer of subsurface material called an aquifer. An aquifer would MOST likely be made of which types of materials? A) gravel and sand
B) clay and silt
C) granite and basalt
D) marble and schist

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Identify the examples in which sam interacts only with natural resources

8) animals respond in various ways to stimuli detected through their senses. some of these responses are stimulated by the presence of danger. which of these animal responses is the best example of a response to an immediate threat? a) a rooster crows every morning at the first sign of light. b) as something approaches an octopus, it shoots a cloud of ink. c) from late fall until spring, bears hibernate to preserve energy. d) a dog is getting hot in the sunlight, so he moves to a shaded area.