In the following number series, one term is missing. Observe the descending pattern in 219, 211, 204, 198, ?, 189 and choose the correct alternative that completes the series.

Introduction / Context:
This question involves a decreasing number series. The given sequence is 219, 211, 204, 198, ?, 189. The challenge is to detect the rule governing the step-by-step decrease and then identify the missing term. Such questions test how well the candidate can work with differences and recognise simple patterns in subtraction.

Given Data / Assumptions:
Series: 219, 211, 204, 198, ?, 189.
One term is missing between 198 and 189.
The series is strictly decreasing overall.
We assume that the same rule is used at each step to move from one term to the next.

Concept / Approach:
Because the series is decreasing, we start by calculating the differences between successive known terms. If these differences themselves follow a pattern, such as descending or ascending by 1, we can extend them to the missing position. This approach is standard in questions where the numbers fall steadily rather than grow.

Step-by-Step Solution:
First difference: 219 - 211 = 8. Second difference: 211 - 204 = 7. Third difference: 204 - 198 = 6. The differences so far are 8, 7, and 6, which are consecutive decreasing integers. Following this pattern, the next difference should be 5, and then 4. So from 198, subtract 5: 198 - 5 = 193 (this is the missing term). Then 193 - 4 = 189, which matches the last given number. Therefore, the missing term is 193.

Verification / Alternative check:
We reconstruct the full sequence: 219, 211, 204, 198, 193, 189. The differences become 8, 7, 6, 5, 4, forming a smooth decreasing sequence. This is a typical pattern used in competitive exam number series. No other candidate number will maintain this consistent drop in the differences, confirming that 193 is the correct value.

Why Other Options Are Wrong:
Option A: 189 repeats the last term too early and gives a difference of 9 from 198, which does not fit the pattern of 8, 7, 6.
Option B: 192 creates a difference of 6 from 198, repeating the previous difference instead of continuing 5 and 4.
Option D: 196 causes a difference of only 2, which breaks the descending sequence of differences.
Option E: 195 gives a difference of 3, again inconsistent with the rule 8, 7, 6, 5, 4.

Common Pitfalls:
A common error is to focus on the values themselves without checking the differences systematically. Another mistake is to miscalculate a difference and then build an incorrect pattern from that error. It is always helpful to write out the differences clearly, observe how they change, and only then extend the pattern to deduce the missing term.

Final Answer:
The only number that maintains the decreasing differences 8, 7, 6, 5, 4 is 193, so the correct option is 193.