Plz with science questions i'm confused

Which are forms of nitrogen that are usable by humans

The leopard frog and the pickerel frog are two closely related species. in areas where their ranges overlap, the frogs will remain separate species if they

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.