Adaface Sample Redux Questions

A developer is working with a Redux application for managing todo items. After some changes to the code, they started facing a problem: When they try to add a new todo item, it doesn't appear on the list. However, deleting a todo item works as expected.
            
            Here is the error message they see in the console when trying to add a todo: `Cannot read property 'undefined' of undefined.`
            
            And here is the relevant Redux code:

Which of the following changes will resolve the issue?

A: Change payload to todo in addTodo action creator.
            B: Change action.todo to action.payload in todoReducer for ADD_TODO case.
            C: Change action.todo to action.payload in todoReducer for ADD_TODO case and change action.index to action.payload for DELETE_TODO case.
            D: Change payload to todo in addTodo action creator and index to payload in deleteTodo action creator.

A developer is working on a Redux application where each action carries an array of items, and each item is an object with an `id` and `value`. The state is an object where each key is an item's `id` and each value is the item's `value`. However, they notice that the `ADD_ITEMS` action isn't updating the state as expected.
            
            Here is the relevant Redux code:

What change should the developer make to correct the issue?

A developer is creating a Redux application to manage a list of blog posts. Each post is represented by an object with id, title, and content properties.
            
            The Redux state should store the post list as an array. The developer observes that the modifications to the posts are not reflecting in the components.
            
            Here is an example of what the state could look like:

Here is the relevant Redux code:

Which of the following changes will resolve the issue?