Refer to the following series and answer the question (all numbers are single digit numbers only).

(Left) 4 2 1 5 7 9 8 7 3 4 3 5 6 2 1 5 1 5 2 8 5 6 9 7 4 7 3 (Right)

How many such odd digits are there each of which is immediately preceded by an odd digit and also immediately followed by an even digit?

Given series:

4 2 1 5 7 9 8 7 3 4 3 5 6 2 1 5 1 5 2 8 5 6 9 7 4 7 3

Condition to be checked:

An odd digit that is immediately preceded by an odd digit and also immediately followed by an even digit.

Odd digit → Odd digit → Even digit

Let's check each odd digit in the series:

4 2 1 5 7 9 8 7 3 4 3 5 6 2 1 5 1 5 2 8 5 6 9 7 4 7 3

The following triplets satisfy the condition:

7 9 8

7 3 4

3 5 6

1 5 2

9 7 4

There are 5 such odd digits.

Hence, "Option 3" is the correct answer.

Mistake Points

Immediately preceded by means immediately before or to come just before.

Immediately followed by means immediately after or to come just after.