Phylum. The classification system goes: Kingdom, Phylum, Class, Order, Family, Genus, Species. Anything that shares a class also share anything above it.
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.
There are a couple reasons the ice is important to polar bears, but given the choices you have the correct one would be:
A. The polar bears can’t out swim the seals, so they sit quietly on an ice platform and attack the seals when they come up for air.
The second phage of cellular respiration is transition stage.
Process take place in transition stage:
The transition stage take place in mitochondria. The pyruvate is combined with NAD+ to form NADH and acetyl co-enzyme molecules.
After transition stage, Krebs cycle starts.