Answer:
"a period change"
Step-by-step explanation:
Simple ways of understanding transformations are:
Phase shift: 2 graphs would be shifted version of each other, all other things constant.
Period change: the 2 graphs would have different cycles, one would be compressed/stretched version of the other, all other things constant
Amplitude Change: The height/crest of the graphs would vary, that is the amplitude. All other things constant.
Addition of Negative constant: this would shift the 1 graph downwards with respect to the other graph, it is a vertical shift. All other things constant.
Now carefully looking at the 2 graphs given, we can see that the cycles are different. One is a more "relaxed", or "stretched" version of the other. This means, the period is changed.
2nd answer choice is right.