Task: Property Constraint Reasoning (ontology: Sciences/Biology)

The property 'skeleton of' applies to instances of 'anatomical structure', and 'trophoblast island' is a subclass of 'anatomical structure'. Which class can appear as the value of 'skeleton of' for instances of 'trophoblast island'?

A. lipid homeostasis
B. ectodermal placode morphogenesis
C. spermatogonial cell division
D. anatomical structure

Answer: anatomical structure