Answer:
A. Variably expressive and incompletely penetrant
Step-by-step explanation:
Incompletely penetrant is a genetic term which means the genetic trait is visible in a fraction of people.
Variable expressivity is the range of signs and symptoms developed in different people with the same genetic condition.
Only some of the members who have inherited the mutant allele have a second toe longer than the big toe signifies variably expressive trait while the extent of webbing varying signifies incomplete penetrant.