How many even numbers are there in the following sequence of numbers which are immediately followed by an odd number as well as immediately preceded by an even number?
8 6 7 6 8 9 3 2 7 5 3 4 2 2 3 5 5 2 2 8 1 1 9

Options

A. one
B. Two
C. Three
D. Four

Explanation

To solve the problem, we need to identify how many even numbers in the given sequence are immediately preceded by an even number and immediately followed by an odd number. Let's go through the sequence step by step.

**Given Sequence:**
8, 6, 7, 6, 8, 9, 3, 2, 7, 5, 3, 4, 2, 2, 3, 5, 5, 2, 2, 8, 1, 1, 9

**Step 1: Identify the even numbers in the sequence.**
The even numbers in the sequence are: 8, 6, 6, 8, 2, 4, 2, 2, 2, 8.

**Step 2: Check each even number to see if it is preceded by an even number and followed by an odd number.**

1. **8** (index 0): Preceded by none, followed by 6 (even) - **Not counted.**
2. **6** (index 1): Preceded by 8 (even), followed by 7 (odd) - **Counted.**
3. **6** (index 3): Preceded by 7 (odd), followed by 8 (even) - **Not counted.**
4. **8** (index 4): Preceded by 6 (even), followed by 9 (odd) - **Counted.**
5. **2** (index 7): Preceded by 3 (odd), followed by 7 (odd) - **Not counted.**
6. **4** (index 11): Preceded by 3 (odd), followed by 2 (even) - **Not counted.**
7. **2** (index 12): Preceded by 4 (even), followed by 2 (even) - **Not counted.**
8. **2** (index 13): Preceded by 2 (even), followed by 3 (odd) - **Counted.**
9. **2** (index 15): Preceded by 5 (odd), followed by 2 (even) - **Not counted.**
10. **8** (index 18): Preceded by 2 (even), followed by 1 (odd) - **Counted.**

**Step 3: Count the valid even numbers.**
From our checks, the even numbers that meet the criteria are:
- 6 (index 1)
- 8 (index 4)
- 2 (index 13)
- 8 (index 18)

**Total Count: 4**

Thus, the answer is **4**.

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