1. Decreases by 4. (B)
2. The atomic number changes. (B)
3. 56/26 Fe. (C)
4. Potassium-40;t1/2=25 days. (B)
5. Takes place in the upper atmosphere. (A)
The correct answer is A. It is uniform in composition and the parts that make up the mixture can be separated from one another through physical means.
Explanation:
In a homogeneous mixture, components are completely integrated, which means the final substance is uniform and the parts that compose it are not separated. This occurs in milk because this integrates uniformly water, fat, among others, and these elements cannot be observed separately.
Moreover, in mixtures, components can be separated through physical means; for example by heating the substances. This applies to milk because if it is heated water evaporates, and therefore can be separated.
