How frequently can scientists prove that their hypotheses are true?

Which statement correctly describes other ways in which nebulae and stars are different? a. a star always has a higher density than a nebula. b. stars can form inside a nebula but a nebula can never be produced by any star. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star. reset submit

Which of the following statements is true of cells

What characteristic does giardia have that makes it a protist, a characteristic that all other protists have? a. it is a unicellular eukaryote. b. it is a eukaryote that is not an animal, a plant, or a fungus. c. it is parasitic and has flagella. d. it spends part of its time in a body of water.