Answer
(a) There is no highest temperature at which ice can exist.
(b) There is no lowest temperature at which water vapor can exist.
Work Step by Step
(a) There is no highest temperature at which ice can exist. Even at a high temperature, if we increase the pressure enough, then the ice will remain as a solid and not change into a liquid or a gas.
(b) There is no lowest temperature at which water vapor can exist. Even at a very low temperature, if we decrease the pressure enough, the water vapor will not change into a liquid or a solid.
