Answer:
D: Carbon
Explanation:
The periodic table lists all the known elements. When looking at it, the only choice you will find is carbon. Therefore, carbon is the element.
Carbon is also by itself, just C.
Water is H2O, which is a molecule due to the 2 different elements.
Carbon Dioxide is CO2, which is a molecule due to the 2 different elements.
Air is just a mixture of different gas molecules, so therefore it is not an element.
Answer:
FADH2 is a reducing agent.
FAD is an oxidizing agent.
Explanation:
The full form of FAD is flavin adenine dinucleotide. It is mainly a redox-active coenzyme which is associated with the different proteins and is involved with the enzymatic reactions in the metabolism.
FAD is obtained by donating or accepting electrons.
In the citric acid cycle,
succinate + FAD → fumarate + 
Thus we see that FAD is an oxidizing agent while
is a reducing agent.
Water is made of only one molecule which can be chemically separated into hydrogen and oxygen. The answer is D.