Correct Answer: D

Rationale: The most likely cause of the 19-year-old college sophomore's joint pain is Lyme disease. The presentation of a red spot shaped like a target (erythema migrans) that spreads, along with joint pain, is classic for Lyme disease. Additionally, the history of camping in an area known to have ticks and the history of using insect repellent support the likelihood of a tick-borne illness like Lyme disease.

Correct Answer: B

Rationale: The presentation of multiple burning erosions on the shaft of the penis along with tender inguinal adenopathy is indicative of genital herpes caused by the herpes simplex virus (HSV). Primary herpes simplex infection typically presents with painful ulcers and lymphadenopathy. The ulcers are often shallow with well-defined borders and can be associated with systemic symptoms such as fever and malaise. In contrast, primary syphilis is characterized by a painless chancre at the site of infection, usually on the genitals. Chancroid can also present with painful ulcers, but it is less common in developed countries. Gonorrhea typically presents with urethral discharge, dysuria, or other symptoms of urethritis, rather than erosions on the penis shaft.

Correct Answer: D

Rationale: HPV (human papillomavirus) infection is a very common sexually transmitted infection (STI) that can affect both men and women. It is the most common STI in the United States. While most cases of HPV infection are asymptomatic and resolve on their own, certain high-risk strains of HPV can lead to the development of various cancers, including cervical cancer. Therefore, HPV infections do cause a small but important number of cervical cancers, making option D the correct choice. Regular screening, such as Pap smears and HPV testing, are crucial for early detection and effective management of HPV-related abnormalities that could progress to cervical cancer.

Correct Answer: C

Rationale: Marion's presentation of back pain associated with constipation and urinary retention is concerning for cauda equina syndrome. Cauda equina syndrome is a rare but serious condition caused by the compression of the bundle of nerves at the bottom of the spinal cord, known as the cauda equina. This compression can result in a variety of symptoms, including back pain, sciatica, changes in bowel and bladder function (such as constipation and urinary retention), as well as lower extremity weakness or numbness.

Correct Answer: B

Rationale: Research studies have shown that for every increment of 20 mm Hg in systolic blood pressure and 10 mm Hg in diastolic blood pressure, the cardiovascular risk approximately doubles. Therefore, the cardiovascular risk increases by 50% for each increment of 20 mm Hg systolic and 10 mm Hg diastolic in blood pressure. This underlines the importance of maintaining healthy blood pressure levels to reduce the risk of cardiovascular diseases.