Answer:
8 millimeters per second, option A
Explanation:
The initial amount of slushy is of 600 millimeters.
Sean will have finished drinking the slushy when the amount remaining is of 0 millimeters. This happens after 75 seconds.
So, he drinks 600 millimeters in 75 seconds.
The average is given by:
600/75 = 8
8 millimeters per second, option A