Final answer:
The constructor initializes class instances and typically injects dependencies, while ngOnInit is an Angular lifecycle hook called after data-bound properties are set up for more complex initialization logic.
Step-by-step explanation:
The main difference between the constructor and the ngOnInit method in Angular is that the constructor is a default JavaScript feature used for initializing class instances, while ngOnInit is an Angular-specific lifecycle hook. The correct answer to the question is a) The constructor initializes the component, while ngOnInit is called by Angular. The constructor is called when the class is instantiated, which happens when the component is being created, but before Angular performs any additional processing. The purpose of the constructor is typically to inject dependencies and perform simple initializations. The ngOnInit method, on the other hand, is called by Angular after the constructor and after the first data-bound properties of a component are set up. It's a place to put more complex initialization logic that relies on bindings being present, and is suggested for any heavy initializations needed for the component.