Assertion (A) : The total mass of the protons of a boron atom is 6185 times the total mass of electrons.
Reason (R ) : Mass of one proton is 1837 times the mass of electron.

Options

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

Explanation

To solve the assertion and reason question, we need to analyze both statements carefully.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
The assertion states that the total mass of the protons of a boron atom is 6185 times the total mass of electrons.

2. **Determining the Mass of Protons and Electrons**:
- We know that the mass of one proton is approximately 1837 times the mass of one electron.
- A boron atom has 5 protons.

3. **Calculating the Total Mass of Protons**:
- The total mass of protons in a boron atom can be calculated as follows:
\[ \text{Total mass of protons} = \text{Number of protons} \times \text{Mass of one proton} \]
\[ = 5 \times (1837 \times \text{mass of electron}) \]
\[ = 5 \times 1837 \times \text{mass of electron} \]
\[ = 9185 \times \text{mass of electron} \]

4. **Comparing the Masses**:
- The assertion claims that the total mass of protons is 6185 times the mass of electrons. However, we calculated it to be 9185 times the mass of electrons.
- Therefore, the assertion (A) is **false**.

5. **Understanding the Reason (R)**:
The reason states that the mass of one proton is 1837 times the mass of an electron. This is a well-established fact in atomic physics.

6. **Evaluating the Reason**:
- Since the mass of one proton is indeed 1837 times the mass of an electron, the reason (R) is **true**.

### Conclusion:
- Assertion (A) is false.
- Reason (R) is true.

Thus, the correct answer is that Assertion (A) is false, and Reason (R) is true.

### Final Answer:
- Assertion (A) is false, Reason (R) is true.