Answer:
The balloon
Step-by-step explanation:
Since there are 100 cm or 1000 mm in a meter, you can rewrite the dimensions in the following way:
A cube of metal with a volume of 10,000 mm^3
A spherical balloon with a volume of 50,000,000 mm^3
A sample of water with a volume of 1,000 mm^3
Therefore, the balloon clearly has the most volume. Hope this helps!