Answer:
Nitrogen fixation
Explanation:
Certain soil bacteria, e.g., <em>Azobacter spp</em> can combine free nitrogen of the atmosphere with oxygen to form nitrates. This is called <u>nitrogen fixation</u>. Other nitrogen-fixing bacteria such as Rhizobium form symbiotic unions with the roots of leguminous plants called root nodules. They fix nitrogen to form nitrates which are used up by the host plant. Nitrifying soil bacteria, e.g., <em>Nitrobacter </em>convert nitrites to nitrates in a process called <u>nitrification</u>.
Answer:
C. because the common goal of basic science is to understand how things work, whether it is a cell, an organism, or a entire ecosystem.
Cells can not function properly at high temperatures
Answer:
sexual reproduction between two individuals from different continents
Answer:
D. There is no enough oxygen in the culture fluid
Explanation:
The cells in the test tube need to carryout one of the important metabolic processes of living organisms - respiration. The process involves the breakdown of glucose to generate energy for other metabolic processes in the cell.
Respiration can be carried out in the presence of oxygen (aerobic) or in the absence of oxygen (anaerobic). Human cells are primarily aerobic but can carryout respiration anaerobically in the presence of inadequate oxygen.
For aerobic respiration, glucose is broken down in the presence of oxygen to produce carbon-dioxide, water and energy in the form of ATP:

<em>In the absence of oxygen, the glucose becomes converted to lactic acid and a smaller amount of ATP is produced as compared to aerobic respiration.</em>
<em>Hence, lactic acid gradually builds up in the absence of oxygen due to anaerobic respiration.</em>
The correct option is D.