You will be given a definition of a task first, then some input of the task.
You need to answer a given question containing a blank (_). Your answer must be one of the two objects mentioned in the question, for example "trophy" and "suitcase". Your answer must not contain a word that is not present in the question. Please don't use articles (e.g., the, a) before the answer.

I need to teach my cat how to do a handshake. I could use either classical conditioning or operant conditioning. The _ approach is foolproof.
Output:
classical