Which statement describes heterogeneous mixtures? they are made up of two or more pure substances that are not chemically bonded together. they appear uniform, like a pure substance. they have fixed ratios between their components. they are made up of two or more pure substances that can be separated only by chemical processes.

Which greenhouse gas is emitted when burn fossil fuels for energy? a.nitrogen b.oxygen c.carbon dioxide d.helium

Which is not a characteristic of bacteria? a. they are unicellular. b. they are prokaryotic. c. they are the smallest form of life on earth. d. they are multicellular.

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.