**Core Concept**
Post coital bleeding is a symptom that requires immediate evaluation due to its association with several gynecological and obstetric emergencies. The underlying concern is the potential for cancer, particularly cervical cancer, as well as other conditions like endometrial polyps or adenocarcinoma.

**Why the Correct Answer is Right**
The next step in managing post coital bleeding involves a thorough cervical and vaginal examination, followed by a colposcopy. This is because post coital bleeding is a red flag symptom for cervical cancer, and colposcopy allows for a detailed examination of the cervix using a special microscope. During colposcopy, any suspicious areas can be biopsied for histopathological examination.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a Pap smear, although useful for cervical cancer screening, is not the immediate next step in the evaluation of post coital bleeding. The presence of bleeding necessitates a more urgent evaluation.

**Option B:** This option is incorrect because a pelvic ultrasound is more useful for evaluating ovarian or uterine pathology, rather than the immediate concern of cervical cancer.

**Option C:** This option is incorrect because an endometrial biopsy may be useful in evaluating postmenopausal bleeding, but it is not the initial step in evaluating post coital bleeding.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that post coital bleeding is a symptom that requires immediate evaluation, and a colposcopy should be performed as soon as possible. This symptom can be a "red flag" for cervical cancer, and prompt evaluation can significantly impact patient outcomes.

**Correct Answer: B. Pelvic examination and colposcopy.**