Why is gold often found in a pure form in nature

Ascientist wants to test ways to reduce pollution in lake . what is the bestway of doing this

69. air frictionthe velocity of the satellitea. decreases b. increases c. sometimes increases sometimedecreases d. no effect at all70. the unit of gravitational potential energy isa.jouté b.watt c. newtond.pascal71. which of the following is not influenced by a magneta. cobalt b.copper c.irond. nickel72. one joule of work done in one second by unit positive chargea.1 watt b.1 volt c.1 js d. none73. the most deviated colour of light after passing through a prisea. violet b.red c. green d.yellow4. a coin is placed below a beaker fill with water upto 12 cm isdisplaced by water isa. 9cm b.6cmс.3cmd.7cm

The ima of the following pulley system is