Which of the following statements is sufficient to answer the following question?
The simple interest on a sum of money is Rs. 50. What is the sum ?
I. The interest rate is `10%` p.a.
II. The sum earned at simple interest in 10 years.

Options

A. Only I
B. Only II
C. Neither I nor II
D. Both I and II

Explanation

To solve the problem of finding the sum of money based on the given simple interest of Rs. 50, we need to analyze the two statements provided.

### Step-by-Step Solution:

1. **Understanding Simple Interest Formula**:
The formula for calculating simple interest (SI) is:
\[ SI = \frac{P \times R \times T}{100} \]
where:
- \( SI \) = Simple Interest
- \( P \) = Principal amount (the sum of money we want to find)
- \( R \) = Rate of interest (in percentage)
- \( T \) = Time (in years)

2. **Using Statement I**:
The first statement tells us that the interest rate is \( 10\% \) per annum.
- We can substitute \( R = 10 \) into the formula.
- However, we still need the time \( T \) to find \( P \).

3. **Using Statement II**:
The second statement indicates that the sum earned at simple interest is for \( 10 \) years.
- We can substitute \( T = 10 \) into the formula.
- However, we still need the rate \( R \) to find \( P \).

4. **Combining Both Statements**:
Now, if we combine both statements:
- From Statement I, we have \( R = 10\% \).
- From Statement II, we have \( T = 10 \) years.
- We can now substitute both values into the simple interest formula:
\[ 50 = \frac{P \times 10 \times 10}{100} \]
Simplifying this:
\[ 50 = \frac{P \times 100}{100} \]
\[ 50 = P \]
Therefore, the principal amount \( P \) is Rs. 50.

5. **Conclusion**:
To find the sum of money, we need both statements together. Neither statement alone is sufficient to determine the sum.

### Final Answer:
Both statements together are needed to answer the question.