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
The orientation of the SN plane to the FH plane should be: 
Select and explain. 
A. SN plane is 7 degrees upwards anteriorly to FH plane, B. FH plane is 7 degrees upwards anteriorly to SN plane, C. SN plane is 5 degrees upwards anteriorly to FH plane, D. FH plane is 5 degrees upwards anteriorly to SN plane
A: SN plane is 7 degrees upwards anteriorly to FH plane
Answer: A: SN plane is 7 degrees upwards anteriorly to FH plane 
Explanation: An alternative horizontal reference line, easily and reliably detected on cephalometric radiographs, is the line from sella turcica (S) to the junction between the nasal and frontal bones (N). In an average individual, the SN plane is oriented at 6 to 7 degrees upwards anteriorly to the Frankfort plane.
Ref: Contemporary orthodontics, William Proffit, 4th edition page 207