A : Only in low or medium energy nuclear reactions, the number of protons and number of neutrons are separately conserved.
R: In high energy reactions, protons and neutrons can be converted into other particles and a new quantum number, the Baryon number is however, always conserved.

Answer

To solve the assertion and reason question, we will analyze both statements step by step.

### Step 1: Understand the Assertion
The assertion states that "Only in low or medium energy nuclear reactions, the number of protons and the number of neutrons are separately conserved."

- In low or medium energy nuclear reactions, the interactions are typically such that the particles involved (protons and neutrons) do not have enough energy to transform into other types of particles.
- Therefore, both the number of protons (which determines the element) and the number of neutrons (which affects the isotope) remain constant throughout the reaction.

### Step 2: Understand the Reason
The reason states that "In high energy reactions, protons and neutrons can be converted into other particles and a new quantum number, the Baryon number is however, always conserved."

- In high energy nuclear reactions, such as those occurring in particle accelerators or cosmic events, protons and neutrons can indeed be converted into other particles (like pions or kaons).
- Despite this conversion, the Baryon number, which counts the total number of baryons (protons and neutrons) minus the number of antibaryons, remains conserved. This means that while individual protons and neutrons may not be conserved, the overall Baryon number is a conserved quantity.

### Step 3: Evaluate the Statements
Now we need to evaluate the truth of both statements:

- The assertion is **true** because it accurately describes the behavior of protons and neutrons in low or medium energy reactions.
- The reason is also **true** because it correctly explains the behavior of protons and neutrons in high energy reactions and the conservation of Baryon number.

### Step 4: Determine the Relationship
The assertion and reason are both true, but the reason does not provide a correct explanation for the assertion. The assertion discusses conservation in low to medium energy reactions, while the reason addresses high energy reactions.

### Conclusion
- The assertion is true.
- The reason is true but does not explain the assertion.

Thus, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

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