[not at teacher]
"apprehend" as "comprehend" is so dated to my AmE ear that I had forgotten it even could mean that. Additionally, I would never use it because it has the (way) more common use as "to arrest" (eg. "the thief was apprehended"). Additionally, as strange as this may be, since it sounds very similar to "apprehensive", which has a negative connotation, I would avoid using it as "comprehend".