If you wrote the Phillips Curve and said the question was true, you received partial credit. Noting that the government could spread out the painful disinflation over time and thus change the time frame of the costs is true, but you should realize that the ultimate amount of unemployment the country would experience is the same. Lots of people unemployed for a short time is a different cost from some people unemployed persistently, but both hurt the country. However, both of these answers missed the key idea behind the question i.e. that expectations can change. The reason the AS curve slopes upward is because higher output implies lower unemployment.
Lower unemployment means that workers have more bargaining power, etc.
Since the real wage is constant, higher nominal wages lead to higher prices. In order to receive full credit on this question, you needed to give complete explanations of the slopes, as above. Simply saying that P and Y were positively or negatively related is not an explanation. This happens automatically as bondholders sell domestic currency and reduce the money supply, or as the Central Bank contracts the money supply through OMOs. Reducing M shifts the LM curve to the left.