Which of the choices below gives a true example of how a natural resource can be renewed? a. when all of the coal is gone from a mine, new coal can be grown in its place. b. when forests have been cut down, new native trees can be planted. c. when an area's natural gas has been used up, oxygen can replace the gas. d. when the sun is hidden behind clouds, lamps can be used to power solar cells.

Ametal ring 4.20 cm in diameter is placed between the north and south poles of large magnets with the plane of its area perpendicular to the magnetic field. these magnets produce an initial uniform field of 1.12 t between them but are gradually pulled apart, causing this field to remain uniform but decrease steadily at 0.240 t/s . (a) what is the magnitude of the electric field induced in the ring? (b) in which direction (clockwise or counterclockwise) does the current flow as viewed by someone on the south pole of the magnet?