Answer: you would then put more sand on top and wait then a little more water!
Explanation:
Because you have to sublimated the leaves
C. Decreased death rate is the answer
What you meant must be the adaptive advantage of the frogs' lungs. Frogs are considered as amphibians wherein the have this unique ability to reside either on land or in water. Their specialised lungs could be responsible to these which makes them capable of breathing oxygen in water and land.
Mutations are not a mechanism for evolution.