5. Multiclass Classification

Explanations for each answer:

• 1-versus-1 multiclass classifiers is incorrect. A 1-versus-1 multiclass classifier is similar to a 1-versus-all classifier, but it uses a different stack of binary classifiers.
• 1-versus-all multiclass classifiers is incorrect. A 1-versus-all multiclass classifier cannot consist of itself.
• Regression models is incorrect. A 1-versus-all multiclass classifier is made up of binary classifiers.
• Binary classifiers is correct.