The change enablement practice maximizes the number of successful service and product changes by ensuring that risks have been properly assessed, authorized, and managed within a schedule1. Change authorization is the activity of verifying that a proposed change is desirable, viable, and achievable before committing to its implementation2. The change type (standard, normal, or emergency) and model (a predefined approach for handling a specific type of change) is the basis for assigning the change authority (the role that can authorize a change)2. The other statements are incorrect because:

A standard change is a low-risk, pre-authorized change that follows an agreed procedure and does not require authorization at the point of implementation2.

An emergency change is a high-priority change that must be implemented as soon as possible to resolve an incident or implement a security patch2. An emergency change must be authorized by an emergency change authority (ECA), which is usually a subset of the normal change authority (CAB)2.

Ensuring that changes are authorized before their deployment is done by the change enabler (the role that coordinates all aspects of a change)2. References: ITIL Foundation - ITIL 4 Edition, page 16; ITIL® 4 – A Pocket Guide, page 39; ITIL® 4 Practice Guide: Change Enablement, page 7.