Answer: The correct answer is Enzymes.
Process of digestion involves the breakdown of large complex molecules ( like carbohydrates, and proteins) present in the food into smaller soluble molecules ( like glucose and amino acids) that can be absorbed by bloodstream and transported to various body organs.
Protein in the stomach is broken down into amino acids with the help of enzyme called as pepsin ( a protease). It is an endo-peptidase that is produced in the stomach and helps in the digestion of proteins at acidic pH of the stomach ( 1.5 to 2).
Answer:
Natural selection can be described as a phenomenon in which individuals of a population which are better adapted to survive in an environment are favored by nature as compared to the individuals of the population which lack better characteristics to survive in the environment.
Through natural selection, evolution occurs and the allelic frequency changes over a period of time. The process of evolution as well as change in the allelic frequencies does not occur just by a single individual, rather it is a collective effort which takes a lot of time. Hence, we say that natural selection changes the population and not a single individual.
It is important to be logical so that you do not end with an impossible conclusion/solution/answer, but you must be creative so that you can think of different ways to try things to get the result you need/ a new result.
Hope this helps!