What ways will allow you to make a field required? Choose three answers

Answer options:

A.Workflow Rules
B.Field Level Requirements
C.Validation Rules
D.Page Layout

Correct Answer: B, C, and D 
Field Level requirement: This is one of the most restrictive requirements, and it requires the field to be entered all the time, regardless of how the record is saved (i.e. through an integration, the API, mass upload, or through the User Interface). 
Page Layout: This option only makes the field required when the specific page layout for that you set this requirement is accessed. This requirement only applies when the record is edited on the user interface. When records are updated via API field requirement does not apply.
Validation Rule: You can build more complex validation rules that have conditional statements to meet your business needs. 
Option A is incorrect because workflows don’t have the option to make a field required. We can have field updates, email notifications, etc. but not making any field required. 
Reference: 

https://help.salesforce.com/articleView?id=000323820&type=1