Which of the following is a feature of complete breech presentation?

A complete breech presentation is characterized by the position of the fetus in the uterus such that the buttocks are positioned to deliver first, with both the hips flexed and the knees flexed. This positioning resembles a seated posture where the thighs are drawn up towards the abdomen and the knees are bent.

In this position, the fetal buttocks are down, and the legs are in a flexed arrangement, which is a key hallmark of a complete breech presentation. This contrasts with other types of breech positions, such as frank breech (where the hips are flexed but the knees are extended) or footling breech (where one or both feet are presenting with extended legs).

The visibility of the scalp at the introitus is indicative of a vertex presentation rather than a breech presentation, meaning that the presenting part is either the fetal head or buttocks, not both. Therefore, the definition and distinctive features of complete breech presentation affirm that the correct answer is the one that describes the positioning of both the hips and knees as flexed.