Answer: The correct answer is black because the product of its side and mass is lower.
Explanation: Density of a substance is defined as the mount of matter that can be stored in a given volume.
Mathematically,

As, density is inversely proportional to the volume of the substance.
The substance will be more denser if it has less volume and it will be less denser if the volume is more.
We are given two cubes having different sides.
Volume of the cube is calculated by using the formula:

where, a = side of the cube.
Black: The side of this cube is 2 and volume will be =
Yellow: The side of this cube is 3 and volume will be =
As, the volume of black cube is less. So, this cube will be more denser.
Density of black cube: 
Density of Yellow Cube: 
Hence, black cube will be more denser because the product of its side and mass is lower.
<u>Answer</u>: A) It is a step in glycolysis.
<u>Explanation</u>: <em>Glycolysis</em> is the metabolic process through which <em>glucose molecules</em> are broken down, whereas <em>β-oxidation</em> is the catabolic process through which <em>fatty acid molecules</em> are broken down.
Excretion<span> is the process of elimination of waste materials from the body. </span>Excretion<span>in </span>plants<span> is much simpler than that of animals and as such it </span>does not pose<span> any serious </span>problem in plants<span>. ... </span>Plants<span> use much of the waste products of catabolism in their anabolic process.</span>
I will answer this if I find the answer.