Final answer:
There are 9 essential amino acids that the human body cannot synthesize and must be obtained from the diet, making option c (9) the correct answer.
Step-by-step explanation:
The human body requires various amino acids to form the proteins necessary for bodily functions. Of the 20 amino acids needed, there are a specific number that the body cannot synthesize on its own and therefore must be obtained through diet. These are known as the essential amino acids.
According to the information provided, the correct number of essential amino acids that the body cannot synthesize and must be obtained from the diet is nine. This makes option c (9) the correct answer to the student's question. It is important to consume a diet that includes these essential amino acids as the body does not store excess amino acids like it does with carbohydrates and fats.
The body requires 20 different amino acids to form proteins, but not all of them are labeled as essential amino acids. The essential amino acids are the ones that the body cannot synthesize and must be obtained from the diet. There are 9 essential amino acids, making option c. 9 the correct answer.