If there is a possibility of four different genotypes in the offspring that result from a dominant-recessive inheritance, and if the couple has four children, would they definitely have children with one expressing each genotype?

yes

Explanation:

they would have one expressing each genotype either in the first cross or second or third

The ability of water to freeze and float on top of the liquid is extremely biologically relevant as it provides a habitat for arctic animals and also allows for life to continue under the polar ice sheets as denser water sinks while freezing water moves up.