That would be A. Photosynthesis.
Answer and Explanation:
Observing population directly gives you accurate result .
Direct observation does not need any intermediary as they themselves go for survey.
So, it is cost efficient.
Whereas indirect observing may involve manipulations.
It requires someone or many to hire who helps in surveying.
It incurs cost.
Thus, direct observation is always better than indirect observation.
The answer is it provides us with vitamins. Hope this helps.
Answer:
Mutations can create entirely new alleles in a population which changes the allele frequencies of a gene pool.
