Discrete series includes items that are exactly measurable and complete. Each unit of data in a discrete series is separate and distinct, with no divisions or intervals. For example, the number of students obtaining specific marks is a discrete series.

Discrete Series:
Discrete series refers to a type of data series that includes items that are exactly measurable and complete. Let's break down why this type of series fits the description given in the question:

Exactly Measurable:
- In a discrete series, each item represents a distinct value or category that can be precisely measured. For example, the number of students in a classroom, the number of cars sold in a month, or the frequency of specific events occurring.
- These items are usually countable and do not involve continuous measurements.

Complete:
- Discrete series include all possible values within a given range or category without any gaps or overlaps. This means that every possible outcome is accounted for in the data set.
- For instance, if we are recording the number of books read by students in a month, the data set would include all the individual counts without missing any values.

Comparison with other types:
- Continuous series, on the other hand, involve measurements that can take any value within a range, making them more fluid and not as clearly defined as discrete series.
- Complex series may involve multiple variables or factors that interact in intricate ways, making them harder to measure and analyze compared to discrete series.
- Simple series may not capture the full range of possible values within a category, unlike discrete series which are comprehensive and inclusive.
In conclusion, discrete series are the most suitable type of data series when dealing with items that are exactly measurable and complete, making them a valuable tool in statistical analysis and research.