Explanation:
<u>Reducing sugars are simple sugars with the ability to reduce copper (II) ions to copper (I). All monosaccharides (fructose, glucose, galactose) are reducing sugars as are some disaccharides, such as lactose and maltose. Simple sugars are all carbohydrates, and are used by the body as a source of energy.</u>

This could be the different times you did the experiment
Answer:
The second one is correct
Explanation:
A leukocyte is responsible for the immune system
Answer: Option D.
Genotype by environment interaction.
Explanation:
Genotype by environment interaction refer to a situation where two different genotypes react differently in an environment. Light skinned humans are at greater risk of skin cancer because they lack melanin which the dark people have and this melanin protect the skin from sun.
All the choices are correct. Differences in the norm of reaction I.e they react different way.
Epistasis is when the effect of a gene suppress the other.
Pleiotrophy is when a gene influence another genes phenotipically. These are all genotype enviromr interaction.