<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 4-week-old Caucasian baby presents for a routine checkup. The patient was born to a 28-year-old G1P1 woman at 38 weeks estimated gestational age by cesarean section secondary to breech presentation. The pregnancy was complicated by gestational diabetes, which the mother controlled with diet and exercise. Prenatal ultrasounds showed normal fetal anatomy. Both parents are nonsmokers. The vital signs include: temperature 37.0C 98.6F, blood pressure 8545 mm Hg, pulse 140min, respiratory rate 42min, and oxygen saturation 99 on room air. Height, weight, and head circumference are within the 90th percentile. Positive Moro and Babinski reflexes are present. The cardiopulmonary examination is normal. While in the supine position, the left leg is visibly shortened relative to the right. When the left hip is abducted with pressure applied to the greater trochanter of the femur, there is a non-tender clunking sound elicited. There is asymmetry of the labial skin folds. A blue macule is noted over the sacral region. Which of the following is the most appropriate next step in the management of this patient?? A: Observation with follow-up in 6 months, B: Magnetic resonance image MRI of the lumbosacral spine, C: Ultrasound of the hips, D: Ultrasound of the lumbosacral spine, E: X-ray of the hips,  <response>: This is a clinical vignette about a 4-week-old infant presenting for a routine checkup. The history and physical exam findings suggest developmental dysplasia of the hip DDH and sacral dimple. The key findings pointing to DDH are the shortened left leg, clunking sound with hip abduction, and asymmetry of labial folds. An ultrasound of the hips would be the most appropriate next step to evaluate for hip dysplasia or dislocation.The sacral dimple could indicate an underlying spinal abnormality, but an ultrasound of the lumbosacral spine would not be appropriate at this age. MRI of the spine could be considered if the sacral dimple was suspicious, but is not the most urgent issue. X-ray of the hips would expose the infant to unnecessary radiation and is not the first-line modality to evaluate for DDH. Observation alone is not adequate given the concerning exam findings.C: Ultrasound of the hips 