Doctors in the early 20th century commonly mistook endometriosis as simple menstrual cramps and informed women that there was no medical cure for their condition.

A. endometriosis as simple menstrual cramps
B. endometriosis for simple menstrual cramps
C. simple menstrual cramps for endometriosis
D. endometriosis to be simple menstrual cramping
E. endometriosis and simple menstrual cramps

OA is B
mistook for or mistook as? PLs, an Expert should do justice to which is correct. Thanks