Explanation
When using a field value variable with a Workflow Action, the exclamation mark (!) will escape the data. A Workflow Action is a custom action that performs a task when you click on a field value in your search results. A Workflow Action can be configured with various options, such as label name, base URL, URI parameters, post arguments, app context, etc. A field value variable is a placeholder for the field value that will be used to replace the variable in the URL or post argument of the Workflow Action. A field value variable is written as fieldname, where field_name is the name of the field whose value will be used. However, if the field value contains special characters that need to be escaped, such as spaces, commas, etc., you can use the exclamation mark (!) before and after the field value variable to escape the data. For example, if you have a field value variable host, you can write it as !$host! to escape any special characters in the host field value.
Therefore, option B is the correct answer.

Reference:
A tag is a descriptive label that you can apply to one or more fields or field values in your events1. You can use tags to simplify your searches by replacing long or complex field names or values with short and simple tags1. To search for events that contain a tag name, you can use the tag keyword followed by an equal sign and the tag name1. You can also use wildcards (*) to match partial tag names1. Therefore, option B is correct because it will return events that contain a tag name that starts with Pri. Options A and D are incorrect because they will only return events that contain an exact tag name match. Option C is incorrect because it will return events that contain a tag name that starts with Priv, not Privileged.

The correct answer is C. Events where values of field A are equal to values of field B.
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 field A match the values for the field B, you can use the following syntax:
| where A=B
This will return only the events where the two fields have the same value.
The other options are not correct because they use different syntax or fields that are not related to the where command. These options are:
* A. Events that contain the string value where A=B: This option uses the string value where A=B as a search term, which is not valid syntax for the where command. This option will return events that have the literal text "where A=B" in them.
* B. Events that contain the string value A=B: This option uses the string value A=B as a search term, which is not valid syntax for the where command. This option will return events that have the literal text
"A=B" in them.
* D. Events where field A contains the string value B: This option uses quotation marks around the value B, which is not valid syntax for comparing fields with the where command. Quotation marks are used to enclose phrases or exact matches in a search2. This option will return events where the field A contains the string value "B".
References:
* where command usage
* Search command cheatsheet