Answer:Reducing mass i.e. water
Step-by-step explanation:
Frequency For given mass in glass is given by
![f=(1)/(2\pi )\sqrt{(k)/(m)}](https://img.qammunity.org/2020/formulas/physics/college/7td4ocswnao9eh7em4c8emux9uynmwonox.png)
where k =stiffness of the glass
m=mass of water in glass
from the above expression we can see that if mass is inversely Proportional to frequency
thus reducing mass we can increase frequency