A helium balloon is secured to a top-pan balance. A metal block with mass $100\text{ g}$ is put onto the balance. The balance shows $91\text{ g}$. Which statement can be inferred from this experiment?
- AThe balloon exerts a downward force of $0.09\text{ N}$ on the top-pan balance.
- BThe helium has a mass of $-9\text{ g}$.
- CThe helium has a mass of $+9\text{ g}$.
- DThe resultant downward force on the top-pan balance is $0.91\text{ N}$.