Explanation
A report is a way to save a search and its results in a format that you can reuse and share with others2. A report is also a type of knowledge object, which is an entity that you create to add knowledge to your data and make it easier to search and analyze2. Therefore, option A is correct. A report can be scheduled, which means that you can configure it to run at regular intervals and send the results to yourself or others via email or other methods2. Therefore, option B is correct. A report can run a script, which means that you can specify a script file to execute when the report runs and use it to perform custom actions or integrations2. Therefore, option C is correct. Therefore, option D is correct because all of the above statements are true for reports.

The correct answer is B. Use the field values in an HTTP error event to create a new ticket in an external system.
A workflow action is a knowledge object that enables a variety of interactions between fields in events and other web resources. Workflow actions can create HTML links, generate HTTP POST requests, or launch secondary searches based on field values1.
There are three types of workflow actions that can be set up using Splunk Web: GET, POST, and Search2.
* GET workflow actions create typical HTML links to do things like perform Google searches on specific values or run domain name queries against external WHOIS databases2.
* POST workflow actions generate an HTTP POST request to a specified URI. This action type enables you to do things like creating entries in external issue management systems using a set of relevant field values2.
* Search workflow actions launch secondary searches that use specific field values from an event, such as a search that looks for the occurrence of specific combinations of ipaddress and http_status field values in your index over a specific time range2.
Therefore, the example that would use a POST workflow action is B. Use the field values in an HTTP error event to create a new ticket in an external system. This example requires sending an HTTP POST request to the URI of the external system with the field values from the event as arguments.
The other examples would use different types of workflow actions. These examples are:
* A. Perform an external IP lookup based on a domain value found in events: This example would use a GET workflow action to create a link to an external IP lookup service with the domain value as a parameter.
* C. Launch secondary Splunk searches that use one or more field values from selected events: This example would use a Search workflow action to run another Splunk search with the field values from the event as search terms.
* D. Open a web browser to look up an HTTP status code: This example would also use a GET workflow
* action to create a link to a web page that explains the meaning of the HTTP status code.
References:
* Splexicon:Workflowaction
* About workflow actions in Splunk Web

The correct answer is B. Pivot1.
In Splunk, Pivot is a tool that uses data models to generate reports and dashboard panels without the need for users to write or understand Splunk's Search Processing Language (SPL)1. Data models enable users of Pivot to create compelling reports and dashboards1. When a Pivot user designs a pivot report, they select the data model that represents the category of event data that they want to work with1. Then they select a dataset within that data model that represents the specific dataset on which they want to report1. This makes Pivot a powerful tool for users who need to create visualizations but do not have a deep understanding of SPL1.

Explanation
The eval command supports a number of functions that you can use in your expressions to perform calculations, conversions, string manipulations and more2. One of the eval command functions is tostring(), which converts a numeric value to a string value2. Therefore, option D is correct, while options A, B and C are incorrect because they are not valid eval command functions.