单项选择题Lateral wall of Ischioanal fossa is:().
A.conjunctive area of inferior fascia of pelvic diaphragm and fascia covering the obturator internus
B.superficial fascia of anal region
C.sphincter ani externus
D.levator ani, coccygeus and inferior fascia of pelvic diaphragm
E.ischial tuberosity, obturator internus and fascia