Answer:
You are going to see the AC functions shifted down
Step-by-step explanation:
Because you had a positive DC signal first, you had to readjust the position to the middle, otherwise, the sum of AC and DC would have been shifted up; because of this, your cursor has been moved down and ones the DC disappears from channel B the signal will be shifted down.
Note: Changing from DC to AC in channel B will kill all the DC signal