The following table is stored in a variable called "dt".

The DataTable object in UiPath is a representation of a table with rows and columns that can store data of various types. It has a Columns property that returns a collection of DataColumn objects that describe the schema of the table1. To extract the column names from a DataTable and store them in a list, you can use the following query:

dt.Columns.Cast(Of Datacolumn).Select(function(x) x.ColumnName).ToList()

This query does the following:

It casts the Columns collection to a generic IEnumerable(Of DataColumn) using the Cast(Of T) extension method2. This is necessary because the Columns collection is a non-generic IEnumerable that cannot be used with LINQ methods directly3.

It selects the ColumnName property of each DataColumn object using the Select extension method and a lambda expression4. The ColumnName property returns the name of the column as a string5.

It converts the resulting IEnumerable(Of String) to a List(Of String) using the ToList extension method6.

The other options are incorrect because:

Option B does not cast the Columns collection to a generic IEnumerable(Of DataColumn), which will cause a runtime error.

Option C uses the AsEnumerable extension method, which returns a collection of DataRow objects, not DataColumn objects7. Therefore, the ColumnName property will not be available.

Option D selects the whole DataColumn object instead of its ColumnName property, which will result in a list of DataColumn objects, not strings.