How many types of joints are there in the human body?
a. 4
b. 2
c. 12
d. 6

There are 6 types of joints found in human body. Hence, the correct answer is d. 6.

1. Pivot joint: These are also called as rotatory joints as they allow rotatory movement. It is found in neck, forearms where it enables the supination and pronation of the forearm.

2. Hinge joint: They are like hinge of the doors and allow the movement in one direction or along one axis only. They are found in ankle, elbow, knees, fingers etc.

3. Saddle joint: These joints provide more stability and flexibility to the joints. For example, carpometacarpal joint of thumb formed by trapzium bone and first metacarpal.

4. Gliding joints: These joints are formed between the bones which meet at nearly flat or flat articlualar surface. They allow the gliding of one over the other in any direction along the plane of the joint.

5. Condyloid joint: Form by the bones which have ovoid articlular surface.

6. Ball and socket joint: Humerus (ball) and cup-like socket of shoulder blade, femur (ball) and socket of the pelvis.