Which of the following are valid options with the chart command?

The choice of "usenull" as a valid option with the chart command is correct because it allows users to specify how to handle NULL values in their resulting chart. When you set usenull to true, the chart command will include NULL values in the output, effectively treating them as a distinct category. This can be particularly useful when you want to visualize how many events fall into the NULL category, which might indicate missing data or values that did not fit into specified groupings.

Understanding the functioning of the chart command is key here. The chart command is used to aggregate data and create statistical charts, and parameters such as usenull enhance its versatility by allowing users to decide how to represent missing or NULL data in their visualizations. This control can significantly influence the insights drawn from the data.

In contrast, the other options do not align with the chart command's capabilities or syntax. For instance, the options like "usefield," "fillfield," and "useother" either do not exist as valid parameters for the chart command or do not apply in the context of data aggregation with charts. Recognizing which options are not applicable is just as critical for mastering the chart command and its parameters in Splunk.