The most significant constituents of coal are .
A: hydrocarbons
B: sulfur
C: oxygen
D: nitrogen
A: hydrocarbons
B: sulfur
C: oxygen
D: nitrogen
举一反三
- （ ）is the most abundant chemical element in plants and animals. A: Oxygen B: Carbon C: Hydrogen D: Nitrogen
- Nitrogen and oxygen are ___ important ___ most living organisms cannot survive without these elements.
- Which elements is not one of the three most common ones in a plant? A: Carbon B: Hydrogen C: Oxygen D: Sulfur
- Which is the most abundant atom (% body weight) in the human body? ( ) A: Hydrogen B: Oxygen C: Carbon D: Nitrogen
- NO的英文名称是_______。 A: nitric oxide B: nitrogen fixation C: nitric acid D: nitrogen oxygen