Final answer:
The types of bones in the human skeleton include long, short, flat, sesamoid, sutural, and irregular bones. Among the options given (a. flat bones, b. short bones, c. sesamoid bones, d. irregular bones), the only type not listed is sesamoid bones.
Step-by-step explanation:
The bones of the skeleton are classified according to their shape, which includes several types. These types are: long bones, which are typically longer than they are wide; short bones, which are roughly cube-shaped; flat bones, which are thin and often provide protection; sesamoid bones, which are embedded within tendons and can vary in size; sutural bones, which are small and located in the skull; and irregular bones, which have complex shapes and do not fit into the other categories.
Based on the options provided in the question, the only type not listed is sesamoid bones. Therefore, the correct answer to the question is:
The bones of the skeleton are classified according to their shape into several categories. These include flat bones, long bones, irregular bones, and short bones. However, the option that is not classified according to shape is sesamoid bones.