Tags are a type of knowledge object that enable you to assign descriptive keywords to events based on the values of their fields. Tags can help you to search more efficiently for groups of event data that share common characteristics, such as functionality, location, priority, etc. For example, you can tag all the IP addresses of your routers as router, and then search for tag=router to find all the events related to your routers. Tags can also help you to normalize data from different sources by using the same tag name for equivalent field values. For example, you can tag the field values error, fail, and critical as severity=high, and then search for severity=high to find all the events with high severity level2
1: Splunk Core Certified Power User Track, page 10. 2: Splunk Documentation, About tags and aliases.

The correct answer is A. | where 10yearAnnerversary=Renewal-MonthYear.
The where command is used to filter the search results based on an expression that evaluates to true or false.
The where command can compare two fields, two values, or a field and a value. The where command can also use functions, operators, and wildcards to create complex expressions1.
The syntax for the where command is:
| where <expression>
The expression can be a comparison, a calculation, a logical operation, or a combination of these. The expression must evaluate to true or false for each event.
To compare two fields with the where command, you need to use the field names without any quotation marks. For example, if you want to find events where the values for the 10yearAnnerversary field match the values for the Renewal-MonthYear field, you can use the following syntax:
| where 10yearAnnerversary=Renewal-MonthYear
This will return only the events where the two fields have the same value.
The other options are not correct because they use quotation marks around the field names, which will cause the where command to interpret them as string values instead of field names. For example, if you use:
| where '10yearAnnerversary'='Renewal-MonthYear'
This will return no events because there are no events where the string value '10yearAnnerversary' is equal to the string value 'Renewal-MonthYear'.
References:
* where command usage

Data model datasets have a hierarchical relationship with each other, meaning they have parent-child relationships. Data models can contain multiple dataset hierarchies. There are three types of dataset hierarchies: event, search, and transaction.
https://docs.splunk.com/Splexicon:Datamodeldataset

The timechart command buckets data in time intervals depending on the selected time range2. The timechart command is similar to the chart command but it automatically groups events into time buckets based on the
_time field2. The size of the time buckets depends on the time range that you select for your search. For example, if you select Last 24 hours as your time range, Splunk will use 30-minute buckets for your timechart. If you select Last 7 days as your time range, Splunk will use 4-hour buckets for your timechart2.
Therefore, option B is correct, while options A and C are incorrect because they are not factors that affect the size of the time buckets.