Long bones are the bones that are longer in length than their width. Examples of long bones include femur, tibia, humerus, and radius. These bones have a unique structure that allows them to perform specific functions. The functions of long bones are as follows:

Support:
Long bones provide structural support to the body. They act as levers and help in the movement of the body. The long bones of the legs support the weight of the body while standing or walking.

Erythrocyte and Leucocyte Synthesis:
Long bones contain bone marrow, which is responsible for the production of red and white blood cells. Red blood cells or erythrocytes transport oxygen to the body tissues, while white blood cells or leucocytes are responsible for fighting infections.

Details of the Function of Long Bones in Erythrocyte and Leucocyte Synthesis:
• The bone marrow is a soft tissue located in the cavities of long bones.
• It is responsible for the production of all types of blood cells.
• Erythrocytes are formed from stem cells in the bone marrow. They mature in the bone marrow before being released into the bloodstream.
• Leucocytes are also formed from stem cells in the bone marrow. They mature in the bone marrow or lymphatic tissue before being released into the bloodstream.
• The bone marrow contains different types of stem cells that can give rise to different types of blood cells.

Conclusion:
Thus, the correct option is B) support, erythrocyte, and leucocyte synthesis. Long bones provide structural support to the body and also play a vital role in the production of red and white blood cells.

1)Long bones provide us support.
2) In long bones lamella is present in that it contains bone marrow.
3) Bone marrow is of 2 type - i] Red bone marrow
ii] yellow bone marrow
4) With the help of red bone marrow Erythrocyte and Leucocyte are produced.