Which of the following would be the least effective option for a user interface design?

A) letting users easily undo their actions or return to previous states
B) making the common tasks very simple to do, so users can accomplish them on the first try without frustration
C) letting users know in an indirect way when something on the website changes, or the user has completed an action
D) avoiding the addition of unnecessary links or options especially when the user is engaged in a sequential task

C