Is it the same capacity?

This task is about capacity.
Teacher Instructions
a) 
Look at the four containers. How many of these containers will hold the same amount of water when they are filled up to the top?
Circle the answer you think is best.

(A)   All of them.          (B)   Three of them.          (C)   Two of them.          (D)   None of them.
 
b)    
Why do you think that?
 
c)   
Fill one container with water and use this to fill the other containers (to show that they are all the same capacity). Then ask:
Why is it that all the containers hold the same amount when they are all different shapes?
 
 
 
 
Student form                      Name: ____________________
 
a)
(A)   All of them.          (B)   Three of them.          (C)   Two of them.          (D)   None of them.   
 
b)
 
 
 
c)
 
 
 
 
Student form                      Name: ____________________
 
a)
(A)   All of them.          (B)   Three of them.          (C)   Two of them.          (D)   None of them.
 
b)
 
 
 
c)