Which statement is used to remove indexes on tables?

Answer: Option A

This question is about how to get rid of indexes in your MySQL database tables. Indexes help your database find information quickly, but sometimes you might need to remove them.

Let's look at the options:
Option A: DROP INDEX - This is the correct answer! "DROP INDEX" is the command in MySQL to remove an index from a table.
Option B: DELETE INDEX - This is incorrect. "DELETE" is used for removing data from a table, not for removing indexes.
Option C: REMOVE INDEX - This is also incorrect. MySQL doesn't use the command "REMOVE INDEX".
Option D: FLUSH INDEX - This is incorrect. "FLUSH INDEX" is used for refreshing the index cache, not removing them.

So, the answer is Option A: DROP INDEX.