Which of the following series of the numbers is in ascending order?

Options

A. 9,7,3,1
B. 1,9,7,3
C. 3,1,7,9
D. 1,3,7,9

Answer

To determine which of the following series of numbers is in ascending order, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Ascending Order**:
- Ascending order means that the numbers are arranged from the smallest to the largest. Each number must be less than or equal to the next number in the series.

2. **Check Option A**:
- The series is 9, 7, 3, 1.
- Compare the numbers:
- 9 is greater than 7 (not in order).
- Since the first number is not smaller than the second, **Option A is not in ascending order**.

3. **Check Option B**:
- The series is 1, 9, 7, 3.
- Compare the numbers:
- 1 is less than 9 (correct).
- 9 is greater than 7 (not in order).
- Since the second number is not smaller than the third, **Option B is not in ascending order**.

4. **Check Option C**:
- The series is 3, 1, 7, 9.
- Compare the numbers:
- 3 is greater than 1 (not in order).
- Since the first number is not smaller than the second, **Option C is not in ascending order**.

5. **Check Option D**:
- The series is 1, 3, 7, 9.
- Compare the numbers:
- 1 is less than 3 (correct).
- 3 is less than 7 (correct).
- 7 is less than 9 (correct).
- Since all comparisons are correct, **Option D is in ascending order**.

### Conclusion:
- The correct option that is in ascending order is **Option D: 1, 3, 7, 9**.