Why is the chemical path nitrogen follows in living systems referred to as a cycle? A) Nitrogen is used and reused.

B) Nitrogen is only used once and destroyed.

C) Circular cells are used to propel the nitrogen along the pathway.

D) The pathway is shaped like a circle.

|using the periodic tablewarm-upuse the periodic table in the tools bar to answer the following questions.what elemental classification does oxygen belongto? done

Sodium sulfate dissolves as follows: na2so4(s) → 2na+(aq) + so42- (aq). how many moles of na2so4 are required to make 1.0 l of solution in which the na concentration is 0.10 m?

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. 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.