To solve this question, the user needs to know about the differences between various SQL commands and their effects on the database.

The ExecuteNonQuery method is used to execute SQL commands that do not return any data. Instead, it is used to execute commands that modify the data in the database.

Now, let's go through each option and explain whether or not it suits the ExecuteNonQuery method:

A. Insert: This option is correct. The Insert command is used to insert new data into a table, which changes the data in the database. Therefore, ExecuteNonQuery is suitable for executing Insert commands.

B. Delete: This option is correct. The Delete command is used to delete data from a table, which changes the data in the database. Therefore, ExecuteNonQuery is suitable for executing Delete commands.

C. Update: This option is correct. The Update command is used to modify existing data in a table, which changes the data in the database. Therefore, ExecuteNonQuery is suitable for executing Update commands.

D. Select: This option is incorrect. The Select command is used to retrieve data from a table and return it to the user. It does not modify the data in the table, so ExecuteNonQuery is not suitable for executing Select commands.

Therefore, the answer is: D.