A resident physician is performing a pelvic examination on a young woman. The fingers of one of her hands are in the patient's vagina, planting the cervix. The other hand is pressing on the abdomen. With the palm of this hand,the physician feels a bony structure in the lower midline. This structure is most likely the
选项：

A:Coccyx;
B:Ilium;
C:Ischium;
D:Pubis;
E:Sacrum