This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
A 10 year old male patient complains of a gap between his upper front teeth. Intra-oral examination reveals a midline diastema of 2 mm, for which a removable appliance with finger springs was given. What type of anchorage is seen with this appliance? 
Select and explain. 
A. Reciprocal, B. Simple, C. Intramaxillary, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: A small but unesthetic diastema (2 mm or less) can be closed in the early mixed dentition by tipping the central incisors together. A maxillary removable appliance with clasps, fingersprings, and possibly an anterior bow will successfully complete this type of treatment.
Reciprocal anchorage: Reciprocal tooth movement is produced when two teeth or resistance units of equal size pull against each other, as in this example of the reciprocal closure of a maxillary midline diastema.
Simple anchorage: Resistance of the anchorage unit to tipping. Closure of a midline diastema can be accomplished with a removable appliance and fingersprings to tip the teeth mesially.
Intramaxillary anchorage: When the anchor units and the reactive units are in the same arch.