Answer:
Four abiotic forms of nitrogen cycle and its chemical formula
Ammonium – 
Ammonia – 
Nitrite –
Nitrate – 
Explanation:
Ammonium: In the nitrogen cycle ammonium is starting point that is present in soil and are converted to various forms by different process.
Ammonia: In the process of nitrogen fixation, the bacteria having nitrogenase enzymes reacts with the nitrogen as well as hydrogen and produces the ammonia, which is further converted to organic compounds.
Nitrite: The nitrosomonas bacteria present helps in conversion of nitrogen gas into nitrite.
Nitrate: Again the Nitrite is converted into Nitrate by the nitrobacter. During the process of assimilation ammonium and nitrate are absorbed by the plants.
Answer:
Xylem cells have no cytoplasm or end walls, meaning they form a tube through which water can pass freely to allow water transport. Lignin strengthens the cell walls, helping to support the plant.
The correct option is THE ELECTRON IN THE OUTERMOST ELECTRON SHELL.
Different levels of energy exist in the atom of an element and these levels are filled with electrons. The electrons in the innermost shell has the lowest energy level while the electrons in the outermost shell has the highest energy level. For an electron to increase its energy level, it has to move to an higher shell; and to decrease its energy level it has to move to a lower shell.
I believe the answer to your question is c