To answer this question, you need to understand what is a procedure stub and what is an object's default event in VB.Net. A procedure stub is a skeleton code that defines the name, parameters, and return type of a procedure, but does not contain any executable statements. An object's default event is the event that is triggered when the user interacts with the object in a common way, such as clicking a button or selecting an item from a list. For example, the default event for a button is the Click event, and the default event for a list box is the SelectedIndexChanged event.

Let's go through each option to understand why it is correct or incorrect:

Option A) Use the Class and Method combo boxes in the Code Editor window. - This option is correct because you can use the Class and Method combo boxes in the Code Editor window to select an object and its default event, and then Visual Studio will automatically generate a procedure stub for you. For example, if you select Button1 and Click from the combo boxes, Visual Studio will create a procedure stub like this:

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

End Sub

Option B) Double click on the object in the Form Designer window. - This option is correct because you can also double click on an object in the Form Designer window to create a procedure stub for its default event. Visual Studio will open the Code Editor window and generate a procedure stub similar to option A.

Option C) Type the procedure declaration in the Code Editor window. - This option is incorrect because typing the procedure declaration in the Code Editor window is not enough to create a procedure stub for an object's default event. You also need to specify which object and event the procedure handles using the Handles keyword. For example, if you type this:

Private Sub Button1_Click(sender As Object, e As EventArgs)

End Sub

You still need to add Handles Button1.Click at the end of the declaration to make it a valid procedure stub.

Option D) Both a and b. - This option is correct because both options A and B are valid ways to write a procedure stub for an object's default event.

Option E) All of the above. - This option is incorrect because it includes option C, which is not a valid way to write a procedure stub for an object's default event.

The correct answer is D. This option is correct because both options A and B are valid ways to write a procedure stub for an object's default event.