Which of the following statements are true regarding digestion and absorption of food in humans>
Oxyntic cells in our stomach secrete the proenzyme pepsinogen.
Fructose and amino acids are absorbed by simple diffusion.
About `30%` of starch is hydrolysed by salivary amylase in our mouth.

Options

A. I and II
B. Only II
C. Only III
D. I and III

Answer

To determine which statements regarding digestion and absorption of food in humans are true, we will evaluate each statement one by one.

### Step-by-Step Solution:

1. **Evaluate the first statement**: "Oxyntic cells in our stomach secrete the proenzyme pepsinogen."
- Oxyntic cells, also known as parietal cells, are responsible for secreting hydrochloric acid and intrinsic factor. However, it is the chief cells in the stomach that secrete the proenzyme pepsinogen, which is then activated to pepsin in the acidic environment of the stomach.
- **Conclusion**: This statement is **false**.

2. **Evaluate the second statement**: "Fructose and amino acids are absorbed by simple diffusion."
- Fructose is absorbed through facilitated diffusion via specific transporters, while amino acids are absorbed through active transport mechanisms, often involving sodium ions as carriers. Therefore, both fructose and amino acids do not simply diffuse across the intestinal mucosa.
- **Conclusion**: This statement is **false**.

3. **Evaluate the third statement**: "About 30% of starch is hydrolyzed by salivary amylase in our mouth."
- Salivary amylase is an enzyme present in saliva that begins the process of starch digestion in the mouth. It is indeed responsible for hydrolyzing approximately 30% of starch into simpler sugars before the food reaches the stomach.
- **Conclusion**: This statement is **true**.

### Final Conclusion:
- The first statement is false.
- The second statement is false.
- The third statement is true.

Thus, the only true statement is the third one regarding the hydrolysis of starch by salivary amylase.