You are working on Azure Data Lake Store Gen1. Suddenly, you realize the need to know the schema of the external data. Which of the following plug-in would you use to know the external data schema?

Answer options:

A.ipv4_lookup
B.mysql_request
C.Pivot
D.Narrow
E.infer_storage_schema 

Correct Answer: E
Option A is incorrect. The ipv4_lookup plugin checks for an IPv4 value in a lookup table and returns the matched rows.
Option B is incorrect. The mysql_request plugin transfers a SQL query to a MySQL Server network endpoint and returns the 1st row set in the result.
Option C is incorrect. Pivot plug-in is used to rotate a table by changing the unique values from 1 column in the input table into a number of different columns in the output table and perform aggregations wherever needed on any remaining column values that are desired in the final output.
Option D is incorrect. This plug-in is used to unpivot a wide table into a table with only three columns.
Option E is correct. infer_storage_schema plug-in can be used to infer the schema of external data and return it as a CSL schema string.
References: 
To know more about the external tables and plug-in, please visit the below-given link: 

https://docs.microsoft.com/en-us/azure/data-explorer/kusto/management/external-tables-azurestorage-azuredatalake
https://docs.microsoft.com/en-us/azure/data-explorer/kusto/query/inferstorageschemaplugin