Task: Class Relation Understanding (ontology: Food_Agriculture/PlantOntology)

Which of the following classes is one valid superclass of 'protonema side branch initial cell'?

A. 1 pattern formation stage
B. 1 root primordium formation stage
C. protonema sub-apical initial cell
D. 2 root meristem formation stage

Answer: protonema sub-apical initial cell