In template-driven forms, default values for form controls are typically set programmatically in the component by initializing the corresponding form control variables with the desired default values. While you can assign values directly in the template, this doesn't allow for dynamic default values or interaction with the component logic. The other options mentioned are not common practices for setting default values in template-driven forms.

The map operator in RxJS primarily transforms data emitted by an Observable. It allows you to apply a function to each item emitted by the source Observable and returns a new Observable with the transformed values.

To build a complex multi-step form with navigation and individual step validation, it's advisable to create separate components for each form step in Angular. This approach promotes code modularity, makes step validation and navigation easier, and improves maintainability. Using a single large form with form groups can become unwieldy, and implementing custom form controls for each step might be overcomplicated. The ngSwitch directive is more for conditionally rendering content than for step navigation.

To define lazy-loaded modules in Angular routes, you use the loadChildren property in the route configuration. This property specifies the path to the module file that should be loaded lazily when the route is activated.

In state management libraries like NgRx or Redux, Selectors are used to listen to changes in a specific slice of the state tree. Selectors allow you to extract and compute derived pieces of state efficiently. They are particularly helpful when you need to extract specific data from your state for presentation purposes or when a component should respond to changes in a specific part of the application state.

To project content into multiple designated spots within a component's template in Angular, you would use multiple tags with select attributes. The select attribute allows you to specify which projected content should go where based on the content's tag or CSS class. and serve different purposes, and is not a valid Angular element.

The ControlValueAccessor interface in Angular includes methods like writeValue, registerOnChange, and setControl. These methods are essential for synchronizing the value of the form control with the native element in the DOM, making it a crucial interface for custom form control development.

The primary purpose of the ControlValueAccessor interface in Angular is to facilitate communication between a custom form control and a form group. It enables the custom form control to integrate seamlessly with Angular's forms module, allowing the form group to manage its value and validation. This interface is essential when creating custom form controls.

The primary difference between structural and attribute directives in Angular is that structural directives change the DOM layout by adding, removing, or replacing elements in the DOM based on conditions. They are typically preceded by an asterisk (*) in their usage, such as *ngIf and *ngFor. In contrast, attribute directives modify the properties or behavior of existing DOM elements, such as changing the color or visibility of an element. They are used without an asterisk in their syntax, like [ngStyle] and [ngClass]. The other options do not accurately describe the difference.

In Angular testing, you typically replace the real service with a "Spy" service. A spy allows you to track calls to service methods, set up return values, and perform other testing-related tasks while avoiding actual service execution.