C.

Pre-molars

A.

Coelomic fluid

The body cavity (coelom) of an earthworm is filled with an alkaline, colourless or milky coelomic fluid containing water, salts, some proteins and four types of coelomic corpuscles, ie, phagocytes, mucocytes, circular nucleated cells and chloragogen cells. The coelomic fluid becomes turgid and acts as a hydraulic skeleton during burrowing.
Earthworm (Pheretime posthuma) living in burrows which are made in moist earth. It makes its burrow which is made in the moist earth. it makes its burrow partly by boring with its pointed anterior end and partly sucking and swallowing the earth. The body shows metameric segmentation. About the middle of each segment, there is a ring of tiny curved bristles called setae or chaetae, formed of any nitrogenous organic substance known as chitin. The setae and musculature serve for locomotion as well as for anchoring body firmly in the burrow.
The blood of earthworm is composed of a fluid plasma and colourless corpuscles, physiologically comparable to the leucocytes of vertebrates.

B.

hinge joint

In hinge joint, the convex surface of one bone fits into the concave surface of another bone. eg, knee elbow and interphalangeal joints.
Pivot joint, one bone is fixed and second articulated, eg, atlas and axial of skull rotate with axis vertebra.
Gliding joints primarily permit side-by-side and back and forth gliding movements, eg, intercarpal joints and intertarsal joints.
In ball and socket joint, a ball of one bone articulates in sockets of another bone, eg, head of the humerus and glenoid cavity of the pectoral girdle.

D.

humerus with scapula

Glenoid cavity articulates humerus with scapula. It is a feature on the scapula (shoulder blade or shoulder bone). It is slightly concave from above downwards and from side to side. It is shallow and a site of attachment of glenoid labrum (glenoid ligament), which forms fibrocartilaginous rim around the glenoid cavity. It is important because it has the effect of depending the socket into which head of humerous (bone) rests, forming the shoulder joint). It represents a type of synovial, ball and socket joint. 

A.

Floating ribs - 2 pairs