The AD curve is generally assumed to have a negative slope. However, which of the following would be sufficient to make the AD curve vertical?

The AD curve is generally assumed to have a negative slope. However, which of the following would be sufficient to make the AD curve vertical? O (a) Consumption is not affected by the real interest rate. O (b) Planned investment is not affected by the real interest rate. (c) Both consumption and planned investment are not affected by the real interest rate. O (d) The central bank does not respond to the inflation rate when setting the real policy rate. O (e) Either (c) or (d) is sufficient