Question

a) what type of rib does the arrow point to? b) which bones does it articulate with? human thoracic cage with arrow pointing to the last bottom rib. floating rib; thoracic vertebra false rib; thoracic vertebra and costal cartilage of rib above true rib; thoracic vertebra and sternum

Explanation:

1. For part A: Floating ribs are the last two pairs of ribs (11th and 12th). They do not attach anteriorly to the sternum or to the costal cartilage of another rib, which is consistent with the rib pointed to in the image.
2. For part B: Floating ribs only articulate posteriorly with the thoracic vertebrae.

Answer:

A. floating rib
B. thoracic vertebra