16. Nitrogen oxidation (nitrification)refers to the
A. conversion of ammonium ions into nitrates through the activities of certain bacteria.
B. changing of atmospheric nitrogen (N2) to nitrogen compounds
C. sulfur is oxidized to the sulfate form through Thiobacillus bacteria
D. none of the above
17. An example of a symbiotic nitrogen fixer is
A. Azotobacter
B. Beijerinckia
C. Clostridium
D. Rhizobium
18. Which of the following is correct?
A. Mycorrhizae are fungi that form a mutually beneficial (symbiotic) relationship with plant roots
B. The fungi aid in transmitting nutrients and water to the plant roots
C. The increased nutrient availability from mycorrhizae is thought to be due to the additional absorbing surface provided by the fungi
D. All of the above
19. In the process of nitrogen fixation, which of the following microorganism is involved?
A. Non symbiotic microorganisms only
B. Symbiotic microorganisms only
C. Non symbiotic and symbiotic microorganisms only
D. None of the above
20. Which of the following statement is not true about the composition of biogas?
A. It is composed almost exclusively of methane and carbon dioxide
B. It also contains with traces of H2S, N2, H2and CO
C. It also contains with traces of O2 and Cl2
D. Both (a) and (b)