Assertion (A) : Honey bee rearing improves the yield beneficial to both from the point of view of crop yield and honey yield .
Reason (R) : Keeping beehives in crop fields during flowering period increases pollination efficiency .

Options

A. Both A and R are correct and R is the correct explanation of A
B. Both A and R are correct but R is not the correct explanation of A
C. A is true but R is false
D. A is false and R is true

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that honey bee rearing improves yield, which benefits both crop yield and honey yield. This implies that having bees around enhances the production of both crops and honey.

2. **Understanding the Reason (R)**:
- The reason provided is that keeping beehives in crop fields during the flowering period increases pollination efficiency. This means that bees help in transferring pollen between flowers, which is crucial for fertilization and subsequently increases the yield of crops.

3. **Explaining Pollination**:
- Pollination is the process where pollen grains from the anthers (male part of the flower) are transferred to the stigma (female part of the flower). This can occur through various agents, including biotic factors like insects (entomophily), which is specifically what bees do.

4. **Role of Bees in Pollination**:
- When bees visit flowers, they collect pollen and nectar. As they move from flower to flower, they inadvertently transfer pollen, which leads to fertilization. This process is vital for the production of fruits and seeds, thus enhancing crop yield.

5. **Impact on Honey Yield**:
- While bees are pollinating flowers, they are also collecting nectar, which they convert into honey. Therefore, as the flowers are pollinated and produce more fruits, the bees also have more nectar to collect, leading to an increase in honey yield.

6. **Conclusion**:
- Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we can conclude that the assertion is supported by the reason. Thus, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
Both Assertion (A) and Reason (R) are true, and the reason is the correct explanation of the assertion.