When we rotate a figure 90° around a point, we need to check the difference in x and y coordinates between the point and the center of rotation.
Then these differences will swap among themselves.
The difference in x-coordinate between A and B is 1, so now this difference will be the difference in y-coordinate.
The difference in y-coordinate between A and B is 7, so now this difference will be the difference in y-coordinate.
So the coordinates of A'' will be:

Also, the point will be in the third quadrant, so all coordinates are negative:

Therefore the answer is C.