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: Gynaecology & Obstetrics
Which of the following is indicated by the term 'mittelschmerz'? 
Select and explain. 
A. Fern pattern of cervical mucus, B. Peritoneal irritation from corpus hemorrhagicum, C. Rise of body temperature due to effect of progesterone, D. LH surge before ovulation
B: Peritoneal irritation from corpus hemorrhagicum
Answer: B: Peritoneal irritation from corpus hemorrhagicum 
Explanation: The follicle that ruptures at the time of ovulation promptly fills with blood, forming what is sometimes called a corpus hemorrhagicum. Minor bleeding from the follicle into the abdominal cavity may cause peritoneal irritation and fleeting lower abdominal pain ("mittelschmerz"). The granulosa and theca cells of the follicle lining promptly begin to proliferate, and the clotted blood is rapidly replaced with yellowish, lipid-rich luteal cells, forming the corpus luteum. Ref: Alford C., Nurudeen S. (2013). Chapter 4. Physiology of Reproduction in Women. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.