This question is incomplete, the missing diagram is uploaded along this question below.
Answer:
Each time you are to decrease the volume by 4 mL
Explanation:
From the image, we can see that the volumes of each syringes are displayed;
the first syringe reads 22
the second syringe reads 18
the third syringe reads 14
the fourth syringe reads 10
and the fifth syringe reads 6
Thus, if we notice the consecutive reading on the syringes, we will notice that each successive step reduces the volume by 4 mL
Therefore, Each time you are to decrease the volume by 4 mL
