Match the following:

Match the following:
| List–I | List–II |
|---|---|
| A. Ball and socket joint | I. Inter carpal joint |
| B. Hinge joint | II. Between humerus and Pectoral girdle |
| C. Pivot joint | III. Between carpals and metacarpals |
| D. Gliding joint | IV. Between atlas and axis |
| V. Knee joint |
Two concentric thin circular rings of radii 50 cm and 40 cm each, carry a current of 3.5 A in opposite directions. If the two rings are coplanar, the net magnetic field due to the two rings at their centre is: