The answer is D. I hope this helps
Answer:Water Only
Explanation:
Given
vessel is insulated therefore no heat can be added or removed i.e. heat exchange is zero
If hot water at
is mixed with cold water at
then at equilibrium vessel contains only water and final temperature of water will be between
and 
Heat released by hot water is equal to heat gain by cold water .
Answer:
Density of unknown liquid is 
Explanation:
When rock is suspended in air then the weight of the rock is counter balanced by the tension force in the string
So here we have

now when the rock is immersed in water then the tension in the string is and buoyancy force due to water is counter balanced by the weight of the object
so here we have



now we have


now when the rock is immersed into other liquid then we have



now we have

