Answer: A
Correct answer: Ctrl + M
Ctrl + M inserts a new slide after the current one, using the same layout unless the previous slide was a title slide, in which case it uses Title and Content. The distractors are all real shortcuts doing something else, and the confusion between them is what the question tests. Ctrl + N creates a new presentation, not a new slide. Ctrl + S saves. Ctrl + D duplicates the selected slide, which is often what is actually wanted when a slide is to be built on the last one. The related shortcuts complete the set: Ctrl + Shift + D also duplicates, Delete removes a selected slide in the thumbnail pane, and Ctrl + Z undoes. Choosing the layout explicitly is done from the New Slide dropdown rather than the shortcut, and it is worth doing - picking the right layout at the start saves rearranging placeholders afterwards.